1.82 Limbic System

Question 1

What are the three pathways that can communicate with the body?

Answer 1

Spinal motor pathways - controlling voluntary, striated muscle
Autonomic motor pathways and adrenaline release - controlling involuntary, smooth muscle
Neuroednocrine pathways form the hypothalamus - physiological and homeostatic pathways

Question 2

What does the hypothalamus control?

Answer 2

Thermoregulation, feeding, drinking and circadian rhythms Growth, metabolism and reproduction
Emotional states - pleasure, rage etc

Question 3

What pathways does the hypothalamus integrate?

Answer 3

• Higher - descending - information from cerebral hemispheres and limbic system
○ Lower- ascending - information from the spinal cord and brain stem
○ Information coming via the blood - hormones, salt, glucose etc.
(somatic/visceral input + blood born signals + central/limbic sytem)

Question 4

What is this intergrated information used for?

Answer 4

• This integrated information is used to coordinate visceral function with appropriate behaviours
e.g. coordination of sexual behaviours with regulation of the gonads and reproductive organs.

Question 5

What do posterior areas of the hypothalamus activate?

Answer 5

Posterior areas of the hypothalamus activate the sympathetic system - fight or flight

Question 6

What do anterior areas of the hypothalamus activate?

Answer 6

The anterior areas o the hypothalamus activate parasympathetic system - rest and digest

Question 7

Where is ADH released from?

Answer 7

posterior pituitary gland

Question 8

Which functions are controlled by the hypothalamus?

Answer 8

1) Regulation of endocrine function
2) Regulation of sexual behaviour
3) Regulation of homeostatic functions
i) Temperature regulation
ii) Regulation of food intake
iii) Regulation of water balance
4) Regulation of visceral function
Regulation of circadian rhythms and sleep-wake cycles

Question 9

Which structure is key in controlling sexual behavior in women?

Answer 9

Ventromedial hypothalamus VMH

Question 10

Which hormone acts upon this structure?

Answer 10

Oestrogen - acts on receptors in VMH - neuronal mechanisms which induce the experession ofsexual behaviour

Question 11

Which male hormone is responsible for male sexual response? And what does it act upon?

Answer 11

Testosterone acts on the preoptic region to produce various characteristic of sexual behaviour

Question 12

How does the hypothalamus control temperature?

Answer 12

Activation of thermoreceptors
		○ Hypothalamus activates trh 
			 Releases tsh then thyroid hormone 
			 Increased metabolic state 
		○ Activation of autonomic mechanisms 
			 Dilate or contrict blood vessels 
		○ Behavioural responses 
Opening windows, putting more clothes on

Question 13

Which parts of the hypothalamus play key roles in feeding?

Answer 13

timulation of the lateral hypothalamus induces feeding behaviour, lesioning produces aphagia
Stimulation of the ventromedial nucleus suppresses feeding behaviour, lesioning produces hyperphagia

Question 14

In terms of feeding, what does the hypothalamus integrate?

Answer 14

It integrates various signals, including gut distention, endocrine signals from the GI tract, sensory stimuli of taste and smell

Question 15

What are circumventricular organs?

Answer 15

Circumventricular organs are several areas of the brainsurrounding the ventricles which lack a normal blood brain barrier

Question 16

Which behavior do these organs help to regulate? And how?

Answer 16

They sense sodium, water and hormone concentrations - coordinate behaviour bu releasing hormones which control kidney diuresis (vasopressin) and sodium excretion (oxytocin)

Question 17

Where are vassopresin and oxytocin released?

Answer 17

They are realeased from the posterior pituitary

Question 18

Which area of the nucleus generates a 24 hour clock?

Answer 18

Suprachiasmatic nucleus - SCN

Question 19

What synchronizes the clock to the day-night cycle?

Answer 19

Light input from optic nerves synchronizes the clock to day and night cycle - jet lat occurs when this is out of phase

Question 20

What other parts can the scn synchronise?

Answer 20

SCN synchronises; hormonal or neural outputs, brainstem, cerebellum, cortex & amygdala

Question 21

What is the function of the pineal gland?

Answer 21

Pineal gland - regulates night time melatonin secretion

Question 22

What are the components of the limbic system?

Answer 22

Amygdala, hippocampus, fornix, mammillary body and septal nuclei

Question 23

What are the major functions of the amygdala?

Answer 23

Emotional learning and memory, fear and fear conditioning, and reward

Question 24

Where is the emotional significance of input assessed?

Answer 24

The emotional significance is assesed in the basolateral nucleus of the amygdala

Question 25

Where do efferents from that area go?

Answer 25

Efferents from there go to the hypothalamus to activate appropriate visceral and motor responses
THEY ALSO GO TO THE ORBITOFRONTAL CORTEX - which mediated the conscious perception of emotion

Question 26

So what is the main function of amygdala?

Answer 26

Linking perception with visceral and behavioural responses and with memory

Question 27

What else involved in fear memory?

Answer 27

Amygdala and medial temporal lobe = mediates acquisition, storage and expression of fear memory

Question 28

What is fear conditioning?

Answer 28

Fear conditioning is a form of emotional learning in which a neural stimulus become associated with an adverse event - presentation of the neural stimulus alone can elicit defensive or fearful behaviour and associated visceral endocrine responses.

Question 29

What forms the reward circuitry?

Answer 29

Nucleus accumbens, spinal nuclei, hippocampus, VTA, amygdala

Question 30

Where can other reward centres be found?

Answer 30

Lateral and ventromedial hypothalamus, amygdala, basal ganglia and ventral tegmental area

Question 31

With which structure do all these structures communicate with?

Answer 31

All of these structures ultimately communicate witht the hypothalamus for neuroendocrine and visceral reward responses

Question 32

Where are important punishment areas found?

Answer 32

Main punishment areas - midrbain and hypothalamus

Less potent punishment areas are found in the amygdala and hippocampus

Question 33

What could stimulation in these areas cause?

Answer 33

It can evoke rage

Question 34

How do tranquilizers work?

Answer 34

Tranquilizers inhibit both the rewars and punishment centres - suroress many behavioural areas - prevent psychotic states - deacreases reactivity

Question 35

What are the symptoms of depression or stressed induced anxiety?

Answer 35

Tired all the time -  muscle ache
		○ Not enjoying things they used to 
		○ Palpitations, dizziness, chest pains, faintness
		○ Poor sleep 
		○ Change in eating pattern 
		○ Trouble concentrating 
Irritable - weepy etc.