101. Assertion: Electrical transmission across a synapse is faster than chemical transmission.
Reason: Electrical synapses are rare in humans.
ⓐ. Both Assertion and Reason are true, and Reason correctly explains Assertion
ⓑ. Both Assertion and Reason are true, but Reason does not explain Assertion
ⓒ. Assertion is true, but Reason is false
ⓓ. Assertion is false, but Reason is true
Correct Answer: Both Assertion and Reason are true, but Reason does not explain Assertion
Explanation: Electrical synaptic transmission is faster since electrical current passes directly between neurons whose membranes lie in very close proximity. Chemical transmission requires additional stages, including transmitter release, movement across the cleft, receptor binding and ion-channel activation. The assertion is true on this mechanistic basis. The reason is also true: electrical synapses are rare in humans. Rarity, however, does not account for transmission speed. It describes occurrence, while speed is explained by the direct current pathway and the absence of the transmitter-mediated sequence. The two statements are related to the same synapse class but do not form a cause-and-explanation pair. Evaluating them requires separating a structural-mechanistic property from a frequency-of-occurrence property.
102. A junction continues to transmit rapidly even after neurotransmitter production in the transmitting neuron is experimentally reduced. Recordings show direct current flow across closely placed membranes. The junction is most consistent with:
ⓐ. a chemical synapse with enhanced vesicle fusion
ⓑ. a non-myelinated axon undergoing continuous conduction
ⓒ. an electrical synapse independent of transmitter release
ⓓ. a post-synaptic membrane lacking any electrical response
Correct Answer: an electrical synapse independent of transmitter release
Explanation: The experiment supplies two decisive observations. Transmission persists despite reduced neurotransmitter production, showing that a chemical messenger is not required for this junction under the stated condition. Direct electrical current is also recorded across membranes that lie in close proximity. Together, these findings identify an electrical synapse. Such transmission resembles direct conduction more closely than the multi-stage mechanism of a chemical synapse and is relatively fast. The observation does not merely describe continuous conduction along one non-myelinated axon; it concerns transfer between communicating cells at a junction. Preserved transmission after transmitter reduction acts as functional evidence, while close membrane placement and direct current provide the structural and mechanistic confirmation. The result identifies the junction by mechanism: preservation of direct current flow despite reduced transmitter production excludes a transmitter-dependent chemical route.
103. Arrange the events of transmission at a chemical synapse.
P. Neurotransmitter binds to specific post-synaptic receptors.
Q. An action potential reaches the pre-synaptic terminal.
R. Ion channels open in the post-synaptic membrane.
S. Synaptic vesicles approach and fuse with the pre-synaptic membrane.
T. Neurotransmitter is released into the synaptic cleft.
ⓐ. Q, T, S, P, R
ⓑ. S, Q, T, R, P
ⓒ. Q, S, P, T, R
ⓓ. Q, S, T, P, R
Correct Answer: Q, S, T, P, R
Explanation: Chemical transmission begins when an action potential reaches the pre-synaptic terminal at Q. This event causes transmitter-filled vesicles to approach and fuse with the pre-synaptic membrane at S. Their contents are released into the synaptic cleft at T. The neurotransmitter then reaches and binds specific receptors on the post-synaptic membrane at P. Receptor activation opens ion channels at R, changing the post-synaptic electrical state and potentially generating an excitatory or inhibitory potential. The order follows the transfer of information from an electrical event in the transmitting neuron to chemical release and then back to an electrical membrane response in the receiving cell. Each stage supplies the condition required for the next one. Reversing fusion and release would be impossible, since transmitter cannot enter the cleft until a vesicle has merged with the pre-synaptic membrane.
104. A treatment prevents synaptic vesicles from fusing with the pre-synaptic membrane. Action potentials still reach the terminal, and the post-synaptic receptors remain functional. The expected result is:
ⓐ. little transmitter release and a reduced post-synaptic response
ⓑ. transmitter diffuses across the cleft despite remaining inside vesicles
ⓒ. direct current crosses the chemical cleft without vesicle fusion
ⓓ. post-synaptic receptors activate before transmitter reaches them
Correct Answer: little transmitter release and a reduced post-synaptic response
Explanation: The terminal action potential is present, so the signal has reached the pre-synaptic side. The blocked step is vesicle fusion with the pre-synaptic membrane. Without fusion, neurotransmitter stored inside the synaptic vesicles cannot be released normally into the fluid-filled cleft. Functional post-synaptic receptors cannot respond to a transmitter that does not reach them, so receptor activation, ion-channel opening and the resulting post-synaptic potential will be reduced. The treatment does not convert the junction into an electrical synapse, since synapse type is not automatically changed by failure of one chemical step. The experiment localises the interruption between terminal excitation and transmitter release while leaving later post-synaptic machinery structurally available but insufficiently stimulated. The intervention acts after axonal conduction but before chemical diffusion across the cleft, locating the failure specifically at the release step.
105. Neurotransmitter is released normally into a chemical synaptic cleft, but a treatment prevents it from binding to post-synaptic receptors. The most direct effect is:
ⓐ. failure of the action potential to reach the pre-synaptic terminal
ⓑ. failure of vesicles to fuse with the pre-synaptic membrane
ⓒ. failure of neurotransmitter to enter the synaptic cleft
ⓓ. failure of receptor-linked ion channels to open normally
Correct Answer: failure of receptor-linked ion channels to open normally
Explanation: Normal release into the cleft shows that the pre-synaptic action potential arrived, synaptic vesicles fused with the pre-synaptic membrane and neurotransmitter entered the extracellular space. The first three stages are therefore functioning. The defect begins when the transmitter reaches the receiving membrane but cannot bind its specific receptors. Receptor binding normally triggers opening of linked ion channels, allowing ion movement to change the post-synaptic membrane potential. Blocking recognition prevents that channel response and reduces the expected excitatory or inhibitory post-synaptic effect. The evidence localises the interruption after transmitter release rather than before it. A failure of terminal excitation, vesicle fusion or release into the cleft would contradict the stated observation that neurotransmitter is already present outside the pre-synaptic cell. The affected step is the conversion of the chemical message into an electrical response at the post-synaptic membrane.
106. Consider the following statements about chemical synaptic transmission.
I. Neurotransmitter is released from the pre-synaptic terminal.
II. Specific receptors occur on the post-synaptic membrane.
III. Receptor activation can open post-synaptic ion channels.
IV. Every post-synaptic potential must produce excitation.
ⓐ. I and IV
ⓑ. I, II and III
ⓒ. II and IV
ⓓ. I, II, III and IV
Correct Answer: I, II and III
Explanation: Chemical transmission has a definite functional orientation. The pre-synaptic terminal stores neurotransmitter in vesicles and releases it into the cleft when an action potential arrives. The transmitter binds specific receptors on the post-synaptic membrane, and receptor activation opens ion channels. Statements I, II and III describe these successive features. Statement IV is too absolute. Ion entry and the resulting post-synaptic potential may promote excitation or inhibit it, depending on the effect produced at the receiving membrane. Chemical transmission is not defined solely by excitation. The valid set preserves the sequence from transmitter release to receptor-linked channel opening while recognising that the biological result can be either excitatory or inhibitory. The valid set includes the common receptor-channel sequence while preserving the important qualifier that the resulting potential may either promote or inhibit excitation.
107. Use the arrangement described below. Structure P is a bulb-like axon terminal containing transmitter-filled vesicles. Space Q is fluid-filled, and membrane R carries specific receptors linked to ion channels. The direction of chemical transmission is:
ⓐ. from P across Q to R
ⓑ. from R across Q to P
ⓒ. from Q into P and then directly into the axon
ⓓ. equally from P and R without a transmitting side
Correct Answer: from P across Q to R
Explanation: Structure P is the pre-synaptic terminal, identified by its position at the end of an axon and by the presence of neurotransmitter-filled vesicles. Space Q is the synaptic cleft separating the two cells. Membrane R is post-synaptic since it contains the specific receptors that respond to the transmitter and activate ion channels. When an action potential reaches P, vesicles release neurotransmitter into Q. The messenger crosses the cleft and binds at R, producing a post-synaptic effect. This unequal distribution of release machinery and receptors establishes functional direction from P to R. The cleft is not itself the source of the signal, and the stated arrangement does not support equal transmission in both directions. The sequence is fixed by the unequal specialisation of the two membranes: vesicle release occurs at P, whereas receptor-mediated reception occurs at R.
108. The table records features of four junctions.
| Junction | Observation | Proposed interpretation |
|---|
| P | Direct current crosses closely placed membranes | Electrical synapse |
| Q | Vesicles release transmitter into a fluid-filled cleft | Chemical synapse |
| R | Released transmitter binds post-synaptic receptors and opens ion channels | Chemical post-synaptic mechanism |
| S | Electrical transmission is slower and commoner than chemical transmission in humans | Electrical-synapse comparison |
Which interpretations are supported?
ⓐ. P and S
ⓑ. Q and S
ⓒ. P, Q and R
ⓓ. P, Q, R and S
Correct Answer: P, Q and R
Explanation: Junction P is correctly interpreted as electrical since current passes directly between membranes in very close proximity. Junction Q has the defining structure and mechanism of a chemical synapse: transmitter-filled vesicles release their contents into a fluid-filled cleft. Record R correctly describes the receiving stage of chemical transmission, where transmitter binds post-synaptic receptors and activates ion channels. Record S reverses both comparative properties. Electrical transmission is faster than chemical transmission, but electrical synapses are rare in humans. The supported set integrates structure, transmitting agent, receptor mechanism, relative speed and occurrence. P, Q and R remain mutually consistent, while S combines two realistic but reversed comparisons and cannot be retained. Record S reverses both supported comparisons: electrical transmission is faster, not slower, and electrical synapses are uncommon rather than common in humans.
109. In a chemical-synapse experiment, transmitter release and receptor binding occur normally. Trial P makes the post-synaptic neuron more likely to become excited, while Trial Q reduces its likelihood of excitation. The recorded potentials are respectively:
ⓐ. inhibitory in both trials
ⓑ. excitatory in both trials
ⓒ. excitatory in P and inhibitory in Q
ⓓ. inhibitory in P and excitatory in Q
Correct Answer: excitatory in P and inhibitory in Q
Explanation: Both trials proceed through the established early stages of chemical transmission: neurotransmitter is released, crosses the synaptic cleft and binds to specific receptors on the post-synaptic membrane. Receptor activation opens ion channels, and the resulting ion movement produces a post-synaptic potential. The biological meaning of that potential is revealed by its effect on excitation. In Trial P, the receiving neuron becomes more likely to be excited, so the potential is excitatory. In Trial Q, excitation is made less likely, so the potential is inhibitory. Chemical transmission does not guarantee one fixed post-synaptic outcome. The same general sequence can end in promotion or inhibition of excitation, and the recorded change in responsiveness distinguishes the two effects. The trials show that successful release and binding do not predetermine the direction of the response; the resulting ion-channel effect determines whether excitation is promoted or inhibited.
110. At a chemical synapse, neurotransmitter binds its post-synaptic receptors and receptor-linked ion channels open. A membrane potential is recorded, but the experiment does not determine whether the receiving neuron becomes more or less likely to be excited. Which conclusion is justified?
ⓐ. A post-synaptic potential formed, but its excitatory or inhibitory character is unresolved
ⓑ. The potential must be excitatory because receptor-linked channels opened
ⓒ. The potential must be inhibitory because the response followed transmitter binding
ⓓ. No post-synaptic potential can form until its effect on excitation is already known
Correct Answer: A post-synaptic potential formed, but its excitatory or inhibitory character is unresolved
Explanation: Transmitter binding and receptor-linked ion-channel opening provide the mechanism needed to alter the electrical state of the post-synaptic membrane. A recorded membrane change therefore supports formation of a post-synaptic potential. The functional classification of that potential requires an additional observation: whether it increases or decreases the likelihood that the receiving neuron will become excited. Channel opening alone does not fix that outcome. Chemical synapses can produce excitatory as well as inhibitory effects, even though both begin with transmitter release, receptor binding and ion movement. The experiment establishes successful chemical reception but does not measure the direction of the change in excitability. Calling the potential necessarily excitatory or necessarily inhibitory would add information not contained in the evidence. The defensible conclusion separates the existence of a post-synaptic electrical response from the later functional interpretation of that response.
111. A transmitter reaches its specific post-synaptic receptor normally, but the receptor-linked ion channels remain closed. Under the stated condition, the most direct consequence is:
ⓐ. an electrical post-synaptic response despite closed receptor-linked channels
ⓑ. a normal post-synaptic potential because transmitter binding is sufficient
ⓒ. a larger post-synaptic potential produced by transmitter concentration alone
ⓓ. failure to generate the expected excitatory or inhibitory post-synaptic potential
Correct Answer: failure to generate the expected excitatory or inhibitory post-synaptic potential
Explanation: The transmitter has crossed the cleft and reached its receptor, so pre-synaptic release and receptor recognition are intact. The interrupted step occurs immediately afterwards. Receptor activation normally opens ion channels in the post-synaptic membrane, allowing ion movement to change the membrane potential. If those channels remain closed, the chemical signal cannot produce its usual electrical effect in the receiving cell. Both possible functional outcomes are affected: the membrane fails to generate the normal potential that would promote excitation or the normal potential that would inhibit it. The junction does not become electrical merely through failure of a chemical step. The evidence localises the defect between receptor binding and the post-synaptic membrane response.
112. Four chemical-synapse records are shown below.
| Record | Observed events | Reported outcome |
|---|
| P | Transmitter binds receptors and ion channels open | Excitation becomes more likely |
| Q | Transmitter binds receptors and ion channels open | Excitation becomes less likely |
| R | No transmitter is released | A normal receptor-mediated potential still appears |
| S | Receptor binding is completely blocked | Normal receptor-linked channel activation occurs |
Which records are internally consistent?
ⓐ. P and R only
ⓑ. P and Q only
ⓒ. Q and S only
ⓓ. P, Q, R and S
Correct Answer: P and Q only
Explanation: Record P is consistent with an excitatory post-synaptic effect. Transmitter binds, channels open and the receiving neuron becomes more likely to be excited. Record Q is also consistent, but the channel-mediated response is inhibitory and makes excitation less likely. These two records demonstrate that the same general chemical-transmission sequence can lead to opposite functional outcomes. Record R lacks transmitter release, so a normal receptor-mediated response is not supported by the stated events. Record S blocks receptor binding yet claims normal receptor-linked channel activation, which breaks the required dependency between recognition and channel opening. The consistent set is identified by tracing the mechanism from transmitter availability through receptor activation to the resulting change in post-synaptic excitability. The inconsistent records claim a normal receptor-mediated response despite removing an essential upstream step. Chemical transmission requires both release and receptor activation before the receiving potential can form.
113. During an intended hand movement, visual information reaches the CNS, a skeletal muscle moves, heartbeat adjusts, and the person later remembers the event. Which interpretation assigns the input, two outputs and higher function consistently?
ⓐ. Central processing receives afferent input, sends somatic output to hand muscle and autonomic output to heart, and supports later memory.
ⓑ. Central processing receives efferent input, sends autonomic output to hand muscle and somatic output to heart, and supports later memory.
ⓒ. Peripheral processing receives afferent input, sends somatic output to hand muscle and autonomic output to heart, and stores later memory.
ⓓ. Central processing receives afferent input, sends autonomic output to hand muscle and somatic output to heart, and supports later memory.
Correct Answer: Central processing receives afferent input, sends somatic output to hand muscle and autonomic output to heart, and supports later memory.
Explanation: Visual information travels towards central processing through an incoming, or afferent, route. The intended movement requires an outgoing command to skeletal muscle, which is somatic efferent output. Adjustment of heartbeat concerns an involuntary organ, so the relevant outgoing control is autonomic rather than somatic. Remembering the event later shows a further contribution of brain processing to higher mental activity; memory is not stored by a peripheral nerve simply because that nerve conveyed an earlier signal. The observations bring together sensory input, different targets for central output and later cognitive processing. The brain contributes to their organisation through several interacting regions and pathways, rather than through one undifferentiated centre that directly performs every function. Identifying the direction of input and the type of each target is necessary to interpret the complete response.
114. Evaluate the following statements about the functions of the brain.
I. It participates in control of voluntary movement and maintenance of balance.
II. It regulates vital involuntary and homeostatic functions.
III. It contributes to approximately \(24\)-hour rhythms and influences several endocrine glands.
IV. Its activity is restricted to movement and excludes memory, emotion and thought.
ⓐ. I and IV
ⓑ. II and IV
ⓒ. I, II and III
ⓓ. I, II, III and IV
Correct Answer: I, II and III
Explanation: Statement I reflects the brain’s role in organising intentional movement and helping maintain body balance. Statement II is also valid, since neural centres contribute to regulation of organs such as the lungs, heart and kidneys and to homeostatic functions including temperature control, hunger and thirst. Statement III adds circadian and endocrine coordination: the brain participates in approximately \(24\)-hour biological rhythms and influences several endocrine glands. Statement IV incorrectly narrows brain function to movement alone. The brain also processes sensory information and supports memory, intelligence, emotions and thought. The valid combination recognises the brain as a multifunctional central organ rather than assigning it one isolated category of control. The fourth statement fails by excluding higher functions that are explicitly part of central processing, including memory, emotion, intelligence and thought.
115. Match each functional group with the activity most directly included in it. A Column II entry is used once.
| Column I | Column II |
|---|
| P. Voluntary movement and balance | 1. Regulation of lungs, heart and kidneys |
| Q. Vital involuntary and homeostatic control | 2. Memory, intelligence, emotion and thought |
| R. Circadian, endocrine and behavioural coordination | 3. Intentional movement with maintenance of body stability |
| S. Sensory and higher mental functions | 4. Approximately \(24\)-hour rhythms and influence on endocrine glands |
ⓐ. P-1, Q-3, R-2, S-4
ⓑ. P-3, Q-1, R-4, S-2
ⓒ. P-4, Q-2, R-1, S-3
ⓓ. P-2, Q-4, R-3, S-1
Correct Answer: P-3, Q-1, R-4, S-2
Explanation: Voluntary movement and balance correspond to intentional motor activity combined with maintenance of body stability, giving P-3. Vital involuntary control includes regulation of organs such as the lungs, heart and kidneys, so Q maps to 1. Circadian and endocrine coordination includes approximately \(24\)-hour rhythms and influence over several endocrine glands, fixing R-4. Sensory and higher mental functions include processing associated with memory, intelligence, emotions and thought, giving S-2. The mapping separates function families that may operate together in daily life but remain biologically distinguishable. A complex action can recruit several groups simultaneously, yet each listed description has one principal functional association in the stated framework. The mapping separates movement-related, involuntary, timing-endocrine and higher-mental roles. Each activity group is identified by the type of regulation involved rather than by anatomical proximity alone.
116. Following a widespread central injury, a person can contract individual muscles when they are directly stimulated, but cannot organise a purposeful sequence of movement and repeatedly loses balance. The findings most strongly support failure of:
ⓐ. peripheral neuromuscular transmission in every tested muscle
ⓑ. central organisation of purposeful movement but not balance
ⓒ. cerebellar balance integration with normal movement planning
ⓓ. brain coordination of voluntary movement and body balance
Correct Answer: brain coordination of voluntary movement and body balance
Explanation: Direct stimulation shows that the muscles retain the ability to contract, so the central problem is not complete loss of muscle function. The major deficits are failure to organise a purposeful sequence and inability to maintain balance. These are coordinated functions rather than isolated contraction events. The brain contributes to planning and control of voluntary movement and to integration required for body stability. A widespread central injury can disrupt that organisation even when individual muscles and some peripheral pathways remain capable of responding. The observations do not establish failure of every synapse, endocrine gland or myelin sheath. The strongest inference stays with the supplied evidence: central coordination of intentional movement and balance has been impaired. Direct muscle stimulation bypasses the damaged central organisation, so preserved contraction cannot establish intact voluntary motor coordination.
117. Study the functional records below.
| Record | Activity | Assigned functional group |
|---|
| P | Regulation of breathing and heartbeat | Vital involuntary control |
| Q | Adjustment of body temperature and urges for food and water | Homeostatic control |
| R | Influence on approximately \(24\)-hour rhythms | Circadian coordination |
| S | Maintenance of balance during walking | Hormone transport |
Which records are appropriately assigned?
ⓐ. P and S
ⓑ. Q and S
ⓒ. P, Q and R
ⓓ. P, Q, R and S
Correct Answer: P, Q and R
Explanation: Record P correctly places breathing and heartbeat among vital involuntary functions regulated through neural centres. Record Q links temperature, hunger and thirst with homeostatic regulation, which maintains internal conditions and adjusts behaviour to physiological needs. Record R appropriately identifies the brain’s involvement in approximately \(24\)-hour biological rhythms. Record S is mismatched. Maintenance of balance is a neural coordination function and is not a form of hormone transport. The table requires comparison across several functional categories rather than recognition of one organ name. P, Q and R preserve the relationship between the observed activity and its broader regulatory role, while S assigns a movement-related function to an unrelated communication mechanism. Record S mismatches the observation and category: maintaining balance belongs to movement coordination, not hormone transport. The remaining rows preserve the stated functional evidence.
118. Peripheral nerves conduct normally, but two selective central disturbances are suspected. Breathing and cardiovascular reflex adjustments are impaired, and body temperature, hunger and thirst have become unstable. Which pair of regions best accounts for the complete pattern?
ⓐ. medulla oblongata and hypothalamus
ⓑ. medulla oblongata and thalamus
ⓒ. pons and hypothalamus
ⓓ. thalamus and cerebellum
Correct Answer: medulla oblongata and hypothalamus
Explanation: The two groups of symptoms point to different central functions. The medulla oblongata contains centres involved in respiratory regulation and cardiovascular reflexes, so its disturbance can account for the changes in breathing and circulatory adjustments. The hypothalamus contains centres involved in body-temperature regulation and the urges for eating and drinking, accounting for the second group. Peripheral nerves are said to conduct normally, which makes a simple loss of peripheral communication insufficient to explain the complete pattern. A thalamic disturbance would principally concern coordination of major sensory and motor signalling, while the pons is described here through its interconnecting tracts. The evidence supports involvement of both a vital involuntary-control region and a homeostatic-control region. It does not require that every function of either region be lost, nor does it justify reducing all the symptoms to one undifferentiated centre.
119. Peak times of the same behavioural activity are recorded under two conditions.
| Condition | Peak times in hours | Ordinary voluntary movement |
|---|
| P. Intact hypothalamic timing | \(0,\ 24,\ 48,\ 72\) | Present |
| Q. After damage to a hypothalamic timing region | \(0,\ 18,\ 45,\ 71\) | Present |
Which inference is best supported by the complete record?
ⓐ. Condition Q retains a precise \(24\)-hour rhythm because voluntary movement is present
ⓑ. P retains circadian periodicity, while hypothalamic damage disorganises timing in Q
ⓒ. matching voluntary movement in both conditions proves identical biological timing
ⓓ. ordinary movement alone is sufficient to preserve circadian timing
Correct Answer: P retains circadian periodicity, while hypothalamic damage disorganises timing in Q
Explanation: Condition P has peaks at \(0,\ 24,\ 48\) and \(72\) hours, so successive peaks are separated by approximately \(24\) hours. That regular interval is the defining evidence for a circadian pattern in the record. In Condition Q, the intervals change to \(18\), \(27\) and \(26\) hours after the hypothalamic timing region is damaged. The activity still occurs and ordinary voluntary movement remains possible, but its repeated timing is no longer regular. The comparison separates biological timing from a general inability to move or perform the behaviour. It supports the role of a hypothalamic region in organising master-clock and circadian control without implying that every hypothalamic function has failed. The conclusion comes from comparing interval regularity across the two conditions, not from the presence or absence of one isolated peak. The irregular intervals in Q are the decisive data; preservation of movement prevents the timing defect from being mistaken for a general loss of behavioural capacity.
120. Assertion: The brain’s influence on human behaviour is unrelated to its roles in circadian and endocrine coordination.
Reason: The brain influences approximately \(24\)-hour rhythms, several endocrine glands and human behaviour.
ⓐ. Both Assertion and Reason are true, and Reason correctly explains Assertion
ⓑ. Both Assertion and Reason are true, but Reason does not explain Assertion
ⓒ. Assertion is true, but Reason is false
ⓓ. Assertion is false, but Reason is true
Correct Answer: Assertion is false, but Reason is true
Explanation: The assertion is false since it artificially separates functions that are all included within the brain’s broad coordinating role. Neural activity contributes to approximately \(24\)-hour rhythms, influences several endocrine glands and participates in human behaviour. These functions need not be identical, but they are not biologically unrelated categories outside central coordination. The reason correctly states the three linked areas of brain influence and directly contradicts the assertion’s claim of complete separation. The truth-value pattern is a false assertion with a true reason. This relation also illustrates that the brain can connect neural, endocrine and behavioural regulation without requiring every effect to occur through the same immediate pathway. The reason does more than contradict the assertion: it places behaviour, circadian timing and endocrine influence within the brain’s broader coordinating activity.
