integrative systems

Question 1

draw a rough diagram of the hypothalmic nuclei

Answer 1

:)

Question 2

what are the functional subdivisions of the hypothalamus?

Answer 2

LATERAL ZONE
– regulation of feeding
– regulation of sleep-awakeness
– integrates info from other hypothalmic nuclei and telencephalic structures engaged in emotions

MIDDLE ZONE
– regulates release of oxytocin and vasopressin from posterior pituitary gland
– regulates ANS
– sets the biological rhythm via its nuclei
– magnocellular secretory system

PARAVENTRICULAR ZONE
– regulates hormone release from anterior pituitary
– parvocellular secretory system

Question 3

describe the blood supply to the hypothalamus

Answer 3

hypothalamic branches off posterior communicating artery supply the hypothalamus

BBB is altered and leaky around hypothalamus as it must detect changes in blood

Question 4

why does the internal carotid artery run through the venous cavernous sinus?

Answer 4

all cranial nerves sit in dura mater to define boundary of cavernous part. abducens nerve located WITHIN cavernous part close to the carotid artery. if internal carotid ruptures, abducens nerve damaged

Question 5

how des the hypophysis develop?

Answer 5

neurohypophysis develops on floor of diencephalon

adenohypophysis develops on roof of mouth

Question 6

how can you use histology to differentiate between the neurohypophysis and adenohypophysis?

Answer 6

adenohypophysis (ant. pituitary) rich in blood vessles

neurohypophysis only contains nerve terminals, no cell bodies

Question 7

which hormones are secreted from the adenohypophysis?

Answer 7

1) growth hormone, GH
2) thyroid stimulating hormone, TSH
3) folicle stimulating hormone, FSH
4) prolactin, PRL
5) adenocorticotrophic hormone, ACTH
6) luteinising hormone, LH
7) melanocyte stimulating hormone, MSH

Question 8

axon terminals in the neurohypophysis are extensions of which nuclei?

Answer 8

paraventricular nuclei → oxytocin

supraoptic nuclei → vasopressin (ADH)

Question 9

TRUE OF FALSE:

the neurohypophysis synthesises and releases hormones

Answer 9

FALSE

the neurohypophysis stores and releases hormones

oxytocin and vasopressin (ADH) are synthesised by hypothalamic neurons

Question 10

function the paraventricular nuclei

Answer 10

located within the hypothalamus

contains magnocellular neurosecretory neurons

regulate hormone release from adrenohypophysis (ant. pituitary)

Question 11

how does the hypothalamus control emotions, learning, and reproductive behaviour?

Answer 11

hypothalamus has bidirectional pathways to limbic structures to control learning, emotions and reproductive behaviour

hypothalamus projects to amygdala via fornix or stria terminalis

hypothalamus connects to septal areas via medial forebrain bundle

Question 12

what is the function of circadian rhythm? what are the components?

Answer 12

circadian clock restricts particular processes to the appropriate time - active phase or inactive phase in a 24 hour cycle

physiological processes occur in response to time cues

components:
• amplitude
• period
• zeitgeber → stimulus that functions as a time cue
• circadian rhythm → rhythm which oscillated with a period of 24 hours in absence of zeitgebers

Question 13

which genes and proteins are particularly important in the cellular clock?

Answer 13

CLOCK

BMAL1

PERIOD (PER)

CRYPTOCHROME (CRY)

Question 14

how is each individual cellular clock kept synchronous?

Answer 14

the SCN (paired nuclei at base of hypothalamus) acts as a “master clock” to keep cellular clocks in synchrony

SCN receives input from retinohypothalmic tract → provides non-visual photic info

projects to many regions:
• ARC → regulates feeding centres
• LHA → secretes neuropeptides which regulate behaviour
• PVN → integrates signals and transmits to brainstem, relaying info to periphery

Question 15

what is the result of a lesion to the SNC

Answer 15

completely arrhythmic sleep cycle

Question 16

describe how physiological processes are regulated in response to light

Answer 16

retinal ganglion cells are stimulated by daylight (blue light)

RGCs activates SCN

SCN increases gene expression of particular proteins

causes regulation of certain physiological processes

during day:
↑ body temp
↑ cortisol hormone
↑ blood pressure
↓ melatonin
↓ GH
↓ testosterone 
↓ prolactin

during night:
↓ body temp
↓ cortisol hormone
↓ blood pressure
↑ melatonin
↑ GH
↑ testosterone 
↑ prolactin

Question 17

how is communication re. the body clock controlled

Answer 17

paraventricular nucleus is the centre of communication

has limbic, hypothalamic, brain stem + peripheral connections

all are time-stamped

Question 18

what happens if the internal body clock is altered?

Answer 18

change to internal clock damages efficiency of hormone release

e.g. blood glucose will remain high for long time —> leads to obesity

Question 19

describe how information travels to regulate melatonin release

Answer 19

melatonin only released at night (time-cue)

1) retina detects light
2) signals to suprachiasmatic nuclei (SCN)
3) SCN sends rhythmic signals to paraventricular nuclei
4) interomediolateral column of spinal cord
5) superior cervical ganglion
6) pineal gland
7) pineal gland releases melatonin
8) neg. feedback causes disinhibition of suprachiasmatic nuclei

LIGHT PERIOD:
• PVN inhibited by GABAergic neurons
• no melatonin release

DARK PERIOD:
• GABAergic neurons silent
• enables excitatory glutamatergic input to stimule PVN
• melatonin release

Question 20

how is learning and memory influenced by circadian clock?

Answer 20

absorb more information during day time

consolidation of memories regulated by internal clock

rats learn conditioning more efficiently at day compared to night