Chapter 4: General Physiology Flashcards
Hindbrain
medulla (natural rhythms)
pons (general awareness/awakeness, simple sensory processes)
cerebellum (muscle coordination)
Midbrain
tectum (auditory)
tegmentum (eye/motor movements)
Forebrain
thalamus (higher input of sensory systems, integrated b/f entering cortex)
hypothalamus (regulator of motivation and emotion)
pituitary gland (send regulatory hormones to this gland which sends other hormones)
basal ganglia (motor control, muscle movement)
limbic system
cerebral cortex (less evolutionary conserved, higher processing of sensory)
Hypothalamus
Responsive to:
Light (photosensitive) –circadian rhythms
Olfactory stimuli (pheromones)
Steroids (reproductive steroids from gonad and adrenal gland)
Neural info (processing of info from CNS & PNS)
Input from autonomic NS
Various peptide hormones and other subs from blood (receiving and regulating)
Hypothalamus
Controls influences upon:
- Autonomic NS
- Hormones from pituitary gland
- Aspects of bodily homeostasis
- Hunger, thirst, sex, maternal behaviour, fear, rage, etc.
Pituitary Gland
Anterior vs Posterior
Hypothalamus controls what hormones this gland releases (via signals)
Anterior (towards front) –connected to hypothalamus thru neuro-secretions (chemical signalling)
Hypothalamus releases hormones into blood, sensed by anterior which releases another hormone
Posterior (back) –made up of nervous tissue, neuronal inputs from hypothalamus (electrical signalling)
Sympathetic NS: flight/fight response
Arousal and energy expenditure (catabolic)
Increase HR and respiratory rate
Increase BP
Inhibits digestion
Decrease blood flow to digestive tract and skin
Increase blood flow to muscle and lungs
Dilation of pupils (take in more light, info from enviro)
Causes epinephrine release from adrenal glands
Piloerection (or goosebumps-hair stand on end –makes us look bigger)
Spontaneous urination and defecation (more common in smaller mammals)
**Response very quick
Parasympathetic NS: rest and digest
Calming, relaxation, energy storage (anabolic)
Decrease HR and respiratory rate Promotes digestion Increased blood flow to digestive tract Stimulates salivary gland secretion Involved in sleep, sexual responses
**Fires slowly
Sympathetic NS Synapsing
Spinal cord: thoracic, lumber
Neuron meets a second neuron, synapse, and then goes to an organ
- 1st neuron=pre-synaptic, 2nd neuron=post-synaptic
Ganglia: group/cluster of nerve cells=sympathetic chain (all neurons leaving the spinal cord in these regions pass thru this chain)
- Some neurons will synapse IN in chain ganglia, other will go through it
o Presynaptic release ACh
o Postsynaptic release norepinephrine
Parasympathetic NS Synapsing
Spinal cord: cranial (nerves), sacral
Nerves leaving the spinal cord synapse again very close to the organs
o Presynaptic release ACh
o Postsynaptic release ACh
Medulla
adrenal gland
rapidly secretes catecholamines into bloodstream in response to systemic NS (epinephrine and norepinephrine)
in response to stress/fear
very quick
Cortex
adrenal gland
slowly secretes steroids (cortisol, DHEA) in response to chemical stimulation (especially ACTH from pituitary)
Hormone
substance released into (and travels thru) the bloodstream that communicates with receptors at some distant site(s)
Neurotransmitter
substance released into the synapse when a presynaptic neuron fires, picked up by a receptor on the dendritic membrane of the postsynaptic neuron, affecting the probability that the postsynaptic neuron will fire
(excitatory or inhibitory influences)
Neuromodulator
substance in brain that changes response of neuron to some other factor
Pheromone
substance emitted or excreted by one individual that affects physiology or behaviour of another member of its species (ex: dog urine marking)
Steroid Hormones
derived from cholesterol
generally slow acting and excreted slowly
small lipid soluble molecules that travel throughout body
act on intracellular receptors
May pass BBB
May bind to carrier proteins in blood
Receptors in various peripheral sites; in the brain predominantly in limbic system
Mainly from: Gonads & Adrenal cortex
Functions include reproduction, stress, and metabolism
Peptide Hormones
consist of various chains of aa derived from pr-
generally fast acting and excreted quickly
large fragile & water soluble
act on extracellular receptors
Do NOT pass BBB
Produced mostly from: Hypothalamus, Anterior & Posterior Pituitary
Peptides from the pituitary control the gonads, adrenal cortex, and thyroid
The anterior pituitary is controlled chemically by peptides in local circulation from hypothalamus
There are many peripheral peptides with relevance to behaviour:
• Insulin and glucagon from pancreas
• CCK & ghrelin from gut
• Leptin from adipose cells
Do not flow freely to all parts of the body, often because of large molecular size
Those produced in periphery may not reach the brain
Monoamine Hormones
derived of single aa generally fast acting and excreted quickly very small & water soluble act on extracellular receptors Do NOT pass blood-brain barrier Generally do not reach brain
Catecholamines from adrenal medulla: epinephrine (adrenaline), norepinephrine (noradrenaline)
Indoleamines from pineal gland: melatonin
Monoamine NTs
Derived from single aa
Tryptophan–> indoleamines (5-HT –> melatonin)
Tyrosine –> catecholamines (DA –> NE –> epinephrine)
Catecholamine NTs: dopamine (DA), norepinephrine (NE)
Indoleamine NTs: serotonin (5-HT)
Other: glutamate, GABA, histamine, glycine
Catecholamines
derived from tyrosine Hormones from adrenal medulla: epinephrine, norepinephrine NT: norepinephrine, dopamine • DA is more abundant than NE MAO and COMT degrade these hormones/NTs
Dopamine
Path
Role
produced ventral tegmental area (VTA)
travel to medial forebrain bundle (MFB)
released into nucleus accumbens
DA circuitry is critical in attention, concentration, general arousal, wakefulness, reward, and addiction. Stimulant drugs like amphetamines, cocaine, and Ritalin (methylphenidate) all activate DA systems.
Norepinephrine
Path
Role
produced in locus coeruleus (LC)
medial forebrain bundle (MFB)
limbic system, neocortex
Adrenaline and NE are released as hormones into the bloodstream, facilitating sympathetic reflexes.
Indoleamines
synthesized from tryptophan
- Hormones from pineal: melatonin
- NTs: serotonin
- MAO degrades these hormones/NTs
Serotonin
Path
Role
Concentrated in Raphe nuclei
MFB
Thalamus, Basal Ganglia, Limbic system, Neocortex
highly (but complexly) involved in affect, cognition, arousal, and other processes.
Melatonin
pineal secretes more melatonin in darkness, regulated by suprachiasmatic nucleus of hypothalamus
Large Neutral Amino Acid Transporter
- Supplies large neutral aa to brain, which otherwise does not directly receive them from circulation
- Transports tyrosine, phenylalanine, tryptophan, methionine, and branch-chained aa
- These aa all compete for transporter, so large quantity of one aa can greatly limit the amount of others entering brain
Acetylcholine (ACh)
not derived from aa
Neurotransmitter at neuromuscular junctions, autonomic ganglia, parasympathetic nerve endings, and throughout the CNS (hippocampus, parts of the thalamus, caudate, brain stem, lateral geniculate).
Serotonin, Tryptophan & Diet
sensitive to diet, and people tend to like foods that contain tryptophan and various tryptamines (e.g. chocolate, red wine).
o Tryptophan loading in diet increase serotonin levels
o Serotonin levels decrease after ingestion of aa beverage devoid of tryptophan
o Want to keep aspartame levels down so tryptophan levels are not depleted
