Chemical Control of the Brain Flashcards
Where is the hypothalamus located?
under the thalamus and above the optic chiasm
What are the two hypothalamus hemispheres separated by?
The 3rd ventricle
What are the three principal subdivisions of the hypothalamus?
The periventricular zone, the median zone, and the lateral zone
What subdivision of the hypothalamus is most adjacent to the 3rd ventricle?
The periventricular zone
What kind of neuron is found in the periventricular hypothalamus?
Neurosecretory neurons
Where do neurons project from the periventricular hypothalamus?
The posterior pituitary gland
What NTs are secreted by the hypothalamus?
Vasopressin, oxytocin, cortical reducing hormone (CRH)
What are the roles of the periventricular zone secretions?
Control of circadian rhythms and the ANS
What is the role of the median and lateral divisions of the hypothalamus?
Thirst/Hunger and ANS
What can be said about the positioning of the hypothalamus in relation to the three large brain divisions?
It is adjacent to all 3 of them, it is at the junction
(telencephalon, diencephalon, mesencephalon)
What information does the hypothalamus integrate?
Visceral and emotional
What system is responsible for emotional information found in the hypothalamus?
The limbic system
What does the hypothalamus directly regulate, and what does it regulate through the pituitary gland?
Direct regulation: ANS and brain stem (short term)
Through pituitary: Hormones and blood (long term)
What body systems are the hypothalamus responsible for?
Metabolic system, behaviour system, and the sleep-wake cycle
What three kinds of responses does the hypothalamus coordinate?
Behavioural, autonomic, and neuroendocrine responses
What specific body functions does the hypothalamus regulate? (6)
- Body Temp
- BP (thirst/salt/urination)
- Defensive behaviour (fight or flight)
- Energetic metabolism (hunger/digestion/growth)
- Reproductive behaviour
- Sleep-wake cycle and alertness
What important role does the hypothalamus play in energetic metabolism?
Glucogenesis
What mechanisms does the hypothalamus start to respond to cold temperature?
Shivering/Goose bumps to generate heat
What mechanisms does the hypothalamus start to respond to hot temperature?
Sweating/Flushing
What kind of feedback loop is homeostasis?
Negative feedback loop
What is another term for the posterior lobe of the pituitary?
The neurohypophysis
What classification of secretory neurons is found in the periventricular hypothalamus?
Magnocellular neurons
What is the mechanism of hormone secretion by the periventricular hypothalamus?
Nerve terminals secrete hormones directly into the blood
What hormones do the single network of capillaries use to regulate the body?
Vasopressin (Antidiuretic hormone ADH)
Oxytocin
What is the role of vasopressin?
Antidiuretic to increase blood volume -> pressure
What hormone is responsible for lactation/attachment/uterine contractions?
Oxytocin
How many amino acids is oxytocin composed of?
9
How does oxytocin relate to childbirth?
It is secreted in the final stage and causes the uterus to contract
What triggers the release of oxytocin?
Sensory stimulation (nipple sucking, visual, auditory)
What was an observed role of oxytocin specific to the prairie vole?
Reproductive behaviour
Describe the 5 step positive feedback loops of Oxytocin-mediated birth
- Head of fetus gives sensory input in cervix
- Nerve impulses project to hypothalamus
- Brain stimulates oxytocin release
- Oxytocin is carried by the bloodstream to uterus
- The oxytocin in the cervix stimulates contractions
What is the letdown reflex?
It is when the sensory stimulus in the cortex reaches the hypothalamus for oxytocin release
How are hypothalamic neurons activated in the condition of lowered BP?
Salt-concentration sensitive neurons (that already have vasopressin in them) secrete vasopressin into the bloodstream
How does vasopressin affect the body?
It activates the kidney to secrete renin into the bloodstream
What does renin do?
It creates angiotensin II
What does angiotensin II act on and what does it do?
It acts on the kidneys and blood vessels to increase water retention and blood pressure
What does angiotensin act on in the telencephalon to do?
It actus on the subfornical organ to create a thirst feeling that motivates drinking
What is the name for the anterior lobe of the pituitary?
adenohypophysis
What kind of secretory neurons are found in the adenophysis?
Parvocellular at the periventricular hypothalamus
What hormones do nerve terminals release in the adenohypophysis periventricular layer?
Liberins and statins
How many capillary networks are found on the frontal pituitary gland and what are their roles?
- Portal vein
- Secretory cells sensitive to liberins and statins secrete hormones into the blood
What are liberins and statins responsible for?
They regulate the release of other hormones lower in the hypothalamus
What final hormone is the adenohypophysis responsible for that exerts function on the whole body?
ACTH
What hormone is secreted from parvocellular hypothalamic cells to control pituitary hormone release?
Corticotrophin release hormone (CRH)
What does ACTH stand for?
adrenocorticotropic hormone
What is the HPA axis?
It is the hypothalamus/pituitary/adrenal axis responsible for stress response
When stressed, what does the HPA release from the adrenal gland?
Cortisol
What is the affect of cortisol on the rest of the HPA?
It inhibits ACTH and CRH production
What are bodily effects of having too much long term cortisol release?
Immune function impairment, mood disorders, cardiovascular disease
What is the substance responsible for energy in fight or flight and suppression of immune/inflammatory systems in humans and mice?
Glucocorticoid
What is the mechanism of glucocorticoid?
Is stimulates gluconeogenesis and inhibits glycogen synthesis to make mor energy and lower immune system function
What systems are different in long term stress vs short term stress
In short term stress, the sympathetic nervous system is activated which involves the adrenal medulla and epinephrine norepinephrine.
In the long term stress, the HPA axis is activated and the adrenal cortex released glucocorticoids. the neurohypophysis is also activated to increase BP
What is different in the bodily responses to short term and long term stress?
Short term is higher blood glucose, pressure, metabolism, and breathing
Long term is increase BP and volume, as well as higher glucose but at the expense of immune function
What is bad about excess cortisol?
It can be cytotoxic and lead to neuron death
What happened to subordinate male baboons in Kenya?
They died of stress (hippocampal neurodegeneration)
What happens to prefrontal cortex neurons and hippocampus neurons in response to too much stress? What does it lead to?
They shrink length of dendrites and number of spines through apoptosis. This affects memory and reasoning
What happens to amygdal and orbitofrontal cortex dendrites in response to stress? What does this lead to?
The dendrites here lengthen and increase number of spines which affects fear and anger levels in response to stress
Why is there a bigger emotional response to stimulus when stress is present?
The increase in cortisol creates a limbic system that has an amplified stress response (more dendritic spines and longer dendrites)
What is the posterior pituitary gland responsible for?
Oxytocin (birth/attachment)
Vasopressin (ADH) (BP)
What is the anterior pituitary gland responsible for?
Growth Hormone (GH) (bones)
Thyroid Stimulating Hormone (TH) (Metabolism)
ACTH (corticosteroids)
FSH, LH (sex organs)
Prolactin (milk secretion)
What are the two components of the CNS (they are influenced by the hypothalamus)?
The brain and spinal cord
What is the portion of the peripheral nervous system that the hypothalamus affects? What is the other portion?
There is the autonomic nervous system which is affected by the hypothalamus, and the somatic nervous system
What are the two divisions of the autonomic nervous systems and their general functions?
The sympathetic nervous system (adrenaline / fight and flight
The parasympathetic nervous system (chill)
What does the ANS innervate?
Smooth muscle, cardiac muscle, and gland cells
What nervous system innervates skeletal muscle and has no ganglia?
The somatic motor system
What is the middle of the Autonomic Nervous System
Ganglia
What does the preganglionic fiber leave and synapse on?
It leaves the CNS and synapses the ganglion
What kind of fiber leaves the ganglion in the ANS? Where does it extend to?
Postganglionic fibers begin at the autonomic ganglia and extends to the target organs
What does an increase in sympathetic activity lead to?
Tissue metabolism and alertness increase
What does the parasympathetic division stimulate?
Visceral activity eg. digestion
What neurotransmitters are active in the sympathetic nerve system?
Ach is found preganglionic and norepinephrine is found post ganglionic
Which ganglion are found closer and farther from the CNS/target organs?
The autonomic sympathetic ganglion are found closer to the CNS, and the parasympathetic ganglion are found closer to the target organs
What neurotransmitters are active in the parasympathetic nervous system?
Only acetylcholine is active
How can we describe the spatial organization of ganglion in the parasympathetic nervous system?
They are close to the affected tisues.
Where in the spine is there a higher and lower ratio of ganglia?
In the upper thoracic sympathetic nervous system, almost every preganglionic neuron has its own ganglion, and in the lower thoracic and lumbar sympathetic nervous system, many preganglionic neurons share a ganlion.
What can be said about the preganglionic innervation of the parasympathic nervous system in the thoracic/lumber/sacral spine?
There is only one sacral neuron that innervates the lower body
What is the role of the adrenal medulla?
It is a modified sympathetic ganglion that releases adrenaline into the blood stream in response to preganglionic innervation
How can we describe preganglionic neurotransmitters?
They are all the same (AcH) and acts on nicotinic acetylcholine receptors
What kind of receptors does acetylcholine act on and what is the resulting EPSP description?
Ionotropic receptors that release fast EPSPs
What can we say about postganglionic neurotransmitters?
The sympathetic nervous system releases norepinephrine, and the parasympathetic nervous system releases acetylcholine
What does norepinephrine bind to in the sympathetic tissues?
Alpha/Beta adrenergic receptors that are G-protein coupled)
What does AcH bind to in the parasympathetic postganglionic receptors, and how can they be described?
AcH binds to muscarinic AcH receptors that are G-protein coupled and have slow EPSP and IPSPs. They require usually prolonged activation
When AcH is a tissue affecter in the sympathetic nervous system, what does it innervate?
Sweat glands, smooth muscle
Where do preganglionic fibers originate?
The brain stem and sacral segments of the spinal cord
