Chemical control of brain and behavior Flashcards
What are functional zones of hypothalamus?
lateral, medial and periventricular (cells of this region lie right next to the wall of 3rd ventricle)
What is the main role of hypothalamus?
integrating somatic and visceral responses in accordance with brain’s needs
SCN = suprachaismatic nucleus
receives direct retinal innervation and function to synchronize circadian rhythms with daily light-dark cycles
How hypothalamus controls posterior pitutitary?
magnocellular neurosecretory cells extend axons down the stalk of pituitary and into posterior lobe
What neurohormones are released by magnocellular neurosecretory cells of hypothalamus?
oxytocin (love hormone), vasopression (regulates blood volume and salt concentration -> effects on kidneys)
What happens when there is low blood volume or pressure?
kidneys secrete renin into bloodstream -> renin promotes synthesis of peptide angiotensin II -> neurons in subfornical organ are excited -> this excitation stimulates hypothalamus -> there is increase in vasopressin production and feeling of thirst
How hypothalamus controls anterior pitutitary?
parvocellular neurosecretory cells secrete hormones into specialized capillary beds of hypothalamo-pituitary portal circulation -> these hormones travel to anterior pituitary where they tigger or inhibit hormonal releases
what are hormones of anterior pituitary?
FSH - follicle-stimulating hormone (ovulation)
LH - luteinizing hormone (ovarian/sperm maturation)
TSH - thyroid-stimulating hormone (metabolism)
ACTH - adrenocorticotropic hormone (cortisol secretion)
GH - growth hormone (protein synthesis)
prolactin - milk secretion
How does stress response occur?
1) perviventricular hypothalamus secretes corticotropin-releasing hormones (CRH) into hypothalamo-pituitary portal circulation
2) this realse triggers adrenocorticotropin (ACTH) release from anterior pituitary
3) ACTH promotes cortisol release from adrenal cortex
How are cortisol levels regulated?
They are to some extent self-regulated because cortisol is steroid, meaning it is lipophilic and can cross blood-brain barrier. It interacts with specific receptors which can inhibit CRH release ensuring cortisol levels are not too high.
adrenal insufficiency
when there is not enough cortisol produced
Cushing’s disease
too much ACTH
What is automatic nervous system?
extensive network of interconnected neurons widely distributed throughout the body -> there is sympathetic and parasympathetic division
sympathetic ANS
fight or flight situations -> increased heart rate, blood pressure, depressed digestive functions, mobilised glucose reserves
parasympathetic ANS
rest and digest -> lower heart rate, blood pressure, digestive functions work fine
What are 3 neural outputs of CNS?
1) somatic motor
2) ANS sympathetic
3) ANS parasympathetic
somatic motor system
innervates and commands skeletal muscle fibres -> cell bodies of somatic motor neurons lie within CNS in either ventral horn of spinal cord or the brain stem
automatic ganglia
cell bodies of automatic lower motor neurons lying OUTSIDE CNS
preganglionic neurons
neurons with cell bodies in CNS: spinal cord and brain stem
preganglionic axons of sympathetic division
- middle third of spinal cord
- neurons lie within intermediolateral gray matter of spinal cord
- 4 F: fight, flight, fright, fuck
preganglionic axons of parasympathetic division
- emerge only from brain stem and lowest segments of spinal cord
- travel far
- digesiton, immune responses, energy storage
What types of tissues innervates ANS?
glands, smooth muscles, cardiac muscles
-> secretory glans (saliva)
-> heart and blood vessels
-> bronchi in lungs
-> digestive and metabolic functions of liver, pancreas etc
-> kidney, bladder, intestines etc
-> genitals
What is enteric division of ANS?
relatively independent from the brain -> component neurons lie within the walls of the digestive organs
Who is responsible for controlling ANS?
mainly = hypothalamus; although nucleus of solitary tract (located in medulla) also important
acetylcholine in preganglionic neurotransmitters
important for both sympathetic and parasympathetic divisions of ANS
-> binds to nicotinic ACh receptors which are ACh gated channels and evoke fast excitatory postsynaptic potential
-> also activate muscarininc ACh receptors what are metabotropic receptors (G-protein-coupled) that can cause both opening and closing of ion channels that lead to very slow EPSP and IPSP
acetylcholine in postganglioninc neurotransmitters
parasympathetic release causes local effect; drugs promoting activation of acetylcholine ( or inhibition of norepinephrine) are parasympathomimetic because they mimick activation of parasympathetic ANS
norepinephrine
important for sympathetic spread out realease; drugs promoting activation of norepinephrine (or inhibition of acetylcholine) are sympathomimetic because they mimick activation of sympathetic ANS
what are diffuse modulatory systems of the brain?
sets of small groups of neurons that have widespread influence in the brain -> unlike neurotransmitters, neuromodulators have diffuse effects
locus coeruleus
nucleus in pons involved in stress and panic
synthesis: norepinephrine!
raphe nuclei
control of sleep-wake cycle
synthesis: serotonin
substantia nigra
midbrain -> projections to caudate nucleus and putamen
synthesis: dopamine!
ventral tegmental area
reward system
synthesis: dopamine!
basal forebrain
unknown function -> one of the first to die in Alzheimer’s disease
synthesis: acetylcholine
brain stem complex
pontomesencephalontegmental complex
synthesis: acetylcholine
psychoactive drugs
mind-altering effects
act on all CNS
interfere with chemical synaptic transmission
hallucinogens
chemically ressemble serotonin and act on serotonergic systems
stimulants
affect dopaminergic and noradrenegic systems
