Neurotransmitters and Nervous System Tissues (5) Flashcards
4 Neurotransmitters
Acetylcholine, amino acids, monoamines, peptides
Amino acids
glutamate, GABA, glycine, etc.
many functions
Monoamines
serotonin, histamine, dopamine, epinephrine, norepinephrine, etc.
attention, cognition, emotion
Peptides
endorphin (opioids)
pain
Acetylcholine (ACh)
- released at neuromuscular junction
- synthesized and enclosed in synaptic vesicles
What releases ACh?
-all neurons that stimulate skeletal muscle
-some neurons in autonomic nervous system
What degrades ACh?
acetylcholinesterase (AChE)
Cholinergic synapse
- Choline + acetyl Coa
- combined by choline acetyltransferase (ChAT) to form ACh
- packaged into synaptic vesicle
- exocytosed when AP reached axon terminal
Catecholamines
Start with tyrosine, turn to L-Dopa, turn to catecholamines:
- dopamine
- norepinephrine
- epinephrine
Norepinephrine and dopamine synthesized in __________
axonal terminals
Epinephrine is released by the ___________
adrenal medulla
Catecholamines: What determines the length of the biosyntheitc pathway?
enzymes present in the cell
sensation
awareness of changes in the environment (internal and external)
perception
conscious interpretation of stimuli
perceptual detection
detecting that a stimulus has occurred
i.e. stepped on a stick
magnitude estimation
how much of a stimulus is acting
i.e. does it hurt?
spatial discrimination
identifying the site or pattern stimulus
i.e. where does it hurt
why to receptive fields overlap?
to find exact location of sensation
Sensation in the PNS: Types of receptors
mechanoreceptors
- touch, pressure, vibration, stretch, itch
thermoreceptors
- temperature change
photoreceptors
- light response
chemoreceptors
- smell, taste, blood chemistry
nociceptors
- pain-causing stimuli
How is the spinal cord organized
into “tracts”
- afferent (ascending)
- efferent (effect)
Afferent
sensory pathways; travel toward brain
Efferent
motor pathways; travel away from brain
At spinal cord: information flows out through ________
dorsal root
At spinal cord: information flows in through ________
ventral root
Alpha motor neurons
innervate skeletal muscle
reflex
rapid, predictable motor response to stimulus
may…
- be intrinsic or acquired
- involve only peripheral nerves and the spinal cord
- involve higher brain centers as well
5 components of reflex arc
- receptor
- sensory neuron
- integration center
- motor neuron
- effector
muscle spindles
mechanoreceptors surrounding muscle fibers to tell brain where limbs are oriented
Steps to knee jerk (myotatic) reflex
quadriceps stretches - sensory pathway to spinal cord
- EPSP to quad = contaction
- IPSP to hamstring = relaxes
response - leg pulled forward
(brain also notified)
happens so animal won’t fall over
Golgi Tendon Organ
dendrites embedded in tendon stimulated with excessive tension
- protects muscle from damaging force
tendon
attaches muscle to bone
Golgi tendon reflex (in every muscle)
protects muscles and tendons from damaging stressing forces
- golgi tendon stretched - action potential to spinal cord
during a reflex the excitatory interneuron…
contracts opposing muscle
during a reflex the inhibitory neuron…
decreases contraction of muscle
Brain stem functions
- autonomic function
- subconscious regulation
- vegetative functions
Brain stem: medulla
origin of vagus nerves; motor nerve tracks cross over
- respiration, heart rate, sneezing, swallowing
Brain stem: pons
sleep, respiration, swallowing, hearing, taste, posture, eye movement
Brain stem: 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; many functions
what regulates the pituitary and pineal glands?
hypothalamus
pituitary gland
releases many hormones
pineal gland
releases melatonin
- regulates breeding season
- through linkage to hypothalamus
Melatonin
produced in absence of light; retinal signals to hypothalamus; activated pineal gland
- seasonal cylicity (sheep, horses, poultry, etc.)
cerebellum
sorts and processes signals to maintain balance, posture, and carry out our coordinated movement
(coordinates flight in birds)
reticular formation
- maintains consciousness
- sensation of pain
- subconscious movements
- filters stimuli from inside and outside body
limbic system
several structures; reacts to odors, emotions, memories, arousal
cerebral cortex
higher brain function, cognition, acquiring knowledge, complex though and behavior
central sulcus
divides brain into 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
premotor cortex (PMC)
conscious feedback
supplementary motor area (Supp MA)
coordinate vis past experience; learned responses
ANS: parasympathetic division
keeps body energy use low
- rest and digest
ANS: sympathetic division
promotes adjustments during exercise
- fight or flight
parasympathetic outflow
few cranial nerves
most carried by vagus nerve
some sacral nerves
NT: mostly ACh
sympathetic outflow
thoracic and lumbar regions
ganglia - collection on soma in the PNS
NT at target organ: mostly epinephrine and norepinephrine
ANS Receptor: Cholinergic
bind ACh
- muscarinic: stimulatory or inhibitory
- nicotinic: always stimulatory
ANS Receptor: Adrenergic
effects of norepinephrine binding to
- alpha receptors generally stimulatory
- beta receptors generally inhibitory
Exception: NE binding to beta receptors of the heart is stimulatory
Reduced calcium gives ______ muscle
relaxed
Increased calcium gives ______ muscle
contracted
review activation and deactivation of smooth muscle
last 2 slides lecture 5
