Neurotransmitters and nervous system tissues: part 2

neurotransmitter

acetylcholine, amino acids, monoamines, peptide

acetylcholine

released at neuromuscular junction, synthesized and enclosed in synaptic vesicles, degraded by acetylcholinesterase, released by: all neurons that stimulate skeletal muscle, some neurons in autonomic nervous system

cholinergic synapse

choline and acetyl Coa combined by choline acetyltransferase (ChAT) to form Ach, packaged into synaptic vesicle, when AP reaches axon terminal → exocytased, degraded by acetylcholinesterase

Catecholamines

enzymes present in the cell determine the length of the biosynthetic pathway, norepinephrine and dopamine are synthesized in axonal terminals, epinephrine is released by the adrenal medulla

dopaminergic synapse

synthesized in axon terminal and awaits AP in vesicles, exocytosed, binds receptors on polysynaptic neuron, reuptake mechanisms, degrading in axon terminals

noradrenergic synapse

formed from tyrosine, shared reuptake mechanism with DA, same degrading enzymes, often has cotransmitters; vasopressin, enkephalin, NPY

Sensation in the PNS

sensation in the awareness of changes in the internal and external environment, perception is the conscious interpretation of those stimuli

perceptual detection

detecting that a stimulus has occurred

magnitude estimation

how much of a stimulus is acting

spatial discrimination

identifying the site or pattern stimulus

mechanoreceptors

touch, pressure, vibration, stretch, itch

thermoreceptors

change respond in temperature

photoreceptors

respond to photon

chemoreceptors

respond to chemicals, smell, taste, blood chemistry

Nociceptors

respond to painful stimuli

spinal cord organization

organized into tracts, sensory pathways travel toward brain (afferent), motor pathways travel away from brain (efferent)

Spinal nerves and roots

spinal nerves carry information to and from CNS, named for where they are located

at spinal cord

breaks into branches, information flows in through dorsal root, out through ventral root

dorsal root ganglion

soma for neurons of dorsal root

alpha motor neurons

innervate skeletal muscle

reflex

rapid, predictable motor response to a stimulus, may be inborn or learned, may involve only peripheral nerves and the spinal cord, may involve higher brain centers as well

reflex arc

1. receptor

2. sensory neuron

3. integration center

4. motor neuron

5. effector

receptor

site of stimulus

sensory neuron

transmits the afferent impulse to CNS

integration center

either monosynaptic region or polysynaptic region within the CNS

Motor neuron

conducts efferent impulses from the integration center to an effector

effector

muscle fiber or gland that responds to the efferent impulse

muscle spindles

mechanoreceptors, surround muscle fibers, and when individual fibers contact, bulge outward, tell brain where limbs are oriented

knee jerk reflex

keeps animals from falling over, response - leg pulled forward, brain also notifeied

golgi tendon organ

dendrites embedded in tendon, protects muscle from over stretch tension, stimulated with excessive tension

golgi tendon reflex

protects muscles and tendons from damaging stressing forces, ensures onset and termination of muscle contraction

golgi tendon stretched

action potential to spinal cord

excitatory interneuron

contracts opposing muscle

inhibitory neuron

decreases contraction of the stretched muscle

brain stem

autonomic function, subconscious regulation

medulla

origin of vagus nerves, motor nerve, tracks crossover, respiration, heart rate, sneezing, swallowing

Pons

sleep, respiration, swallowing, hearing, taste, posture, eye movement

midbrain

relay center

thalamus

relays sensory signals, including motor signals, to the cerebral cortex, and the regulation of consciousness, sleep, and alertness

hypothalamus

endocrine regulator, ANS regulator

pituitary

releases many hormones

pineal gland

releases melatonin, regulates breeding season, through linkage to hypothalamus

melatonin

produced in absence of light, retinal signals to hypothalamus, activates pineal gland

cerebellum

“little brain”, sorts and processes signals to maintain balance, posture and carry out our coordinated movement, largest relative part of bird brain (coordinates flight)

reticular formation

maintains consciousness, sensation of pain, subconscious movements, filters stimuli from both inside and outside body

limbic system

several structures (HHAT), reacts to odors, emotions, memories, arousal

cerebral cortex

most recently involved part of brain, outermost 6 layers of neurons, higher brain function, cognition, acquiring knowledge, complex though, complex behavior

central sulcus

divides intro front and back

primary somatosensory

cortex-caudal to central sulcus- neurons firing tells animal a specific body region is being stimulated

primary motor cortex

rostral to central sulcus-neurons firing tell skeletal muscles to move

parasympathetic division

keeps body energy use low, animal after eating: BP, HR, RR are low, Gastrointestinal activity is high, the skin is warm and the pupils are constricted

sympathetic division

fight or flight system, promotes adjustments during exercise - blood flow to organs is reduced; flow to muscles is increased, threatened animal: HR increase, cold and sweaty

parasympathetic outflow

few cranial nerves, most carried by vagus nerve, some sacral nerves, NT: mostly ACh

cholinergic receptors

bind ACh

muscarinic - stimulatory or inhibitory

nicotinic - always stimulatory

adrenergic

alpha and beta - 2 or 3 subclasses, effects of norepinephrine binding to:

alpha receptors are stimulatory

beta receptors are inhibitory

Activation of smooth muscle

sympathetic axon at the artery wall, NE, ATP, and neuropeptide Y

ATP binds receptor

opens calcium and sodium channel —> depolarizes→ opens calcium channel → contraction

NE binds receptor

G-protein coupled → calcium channel opens → contraction

NPY

??? → increase cytosolic calcium → contraction

deactivation of smooth muscle

parasympathetic axon at artery wall, ACh oxide and vasoactive intestinal peptide