Secondary
- Disease: Alzheimer, lewy body dementia, normal hydrocephaly
- Neuron - allows for rapid communication within the body, like a switch on and off - microwave
- whereas hormone as chemical messenger slow to act and persistent within the body - oven
- impulses can propagate in both directions if stimulated midway
- Nervous system organization
- sensor & effector
- Ganglion - a mass of nerve cell bodies
- Nerve fibre - axon of neuron
- Nerve - a bundle nerve fibres within the PNS; while in CNS, referred to as Tract
- sensory, motor and mixed; provide common pathway for electronchemical nerve impulses or action potentials
- CNS - Central nervous system for integration and association
- brain (85 billion neurons) and spinal cord
- Interneuron - has short dendrites and long or short axon, e.g. mirror neuron
- association neurons connecting neurons within the CNS, sensory with motor
- PNS - peripheral nervous system, everything lying outside of CNS.
- Afferent neuron - sensory neuron (division) (affected by) carry impulse / sensory input (touch, taste, smell, sight, hearing; pain, perception of body in space, and balance; receptors in whisker in cats to position) toward the CNS via receptor (specific); Na flows in and generates an impulse migrating the dendrite, to the cell body, out to the axons.
- dendrites near the receptor, then long axons - cell body - axons = shape different from efferent neurons
- Efferent neuron - motor neuron (2 types), effect change (do things), motor output - muscles (voluntary skeletal and involuntary/autonomic - breathing, heart; automatic), glands; can have short axons and long dentrites
- glia - feed, nurture and fix neurons; speed increase
- Somatic nervous system - voluntary - 1 neuron; effector to skeletal (striated) muscle;
- Myelin sheath - plays critical role in impulse conduction and make it faster
- Reflex arc - main functional unit of nervous system, allowing us to react to internal and external stimuli reflexively
- effector stimulated before the brain = respond without going up to the brain, just reach the spinal cord
- Mixed nerve - a bundle of nerve fibre sensor and motor
- Autonomic nervous system - involuntary - 2 neurons (1 short and 1 long in either sequence)
- Parasympathetic nervous system: rest and digest, not paranormal tho
- pupil (iris, pupil size) constrict;
- heart rate decrease; slow and deep breathing rate; constrict bronchi; dilate skin blood vessel
- activation of stomach and intestinal glands; motility of stomach and intestinal wall
- ACh dominates
- from CNS - long preganglionic motor neurons axons and short post preganglionic dentrites (also short axon) connected by ganglion to heart organ (effector) #exam
- at the ganglionic, it's always ACh
- Sympathetic nervous system: fight or flight
- secretion of sweat glands; reverse of parasympathetic
- NAd dominates
- from CNS - short pre axons and long post dendrites (also long axon) to heart organ
- at the ganglionic, it's always ACh
- Sympathetic hormone - Adrenaline from adrenal medulla; aldosterone (regulate Na+) from adrenal cortex
- Enteric nervous system - interneurons as well, known as second brain, 500 million neurons etc
- PNS - sensory + motor (autonomic nervous system, somatic nervous system); connect the body to the autonomic nervous system
- Synapse - gap/cleft/synapse between axon bulb and dendrite
- NT - neurotransmitter, localized hormone; chemical substance diffusing across the synapse; transfer impulse from one to another
- ACh - acetylcholine
- at PNS, associated with rest and digest (parasympathetic) response in ANS involuntary system; associated with skeletal muscle contraction at the neuromuscular junction (axon terminals)
- at CNS, short-term memory or learning, attention, REM sleep
- NAd - NE, norepinephrine (NAd, noradrenaline (adrenaline is hormone though), more Canadian)
- at PNS, associated with fight or flight response (sympathetic)
- Serotonin - associated with ability to deal with depression; high ones - feel good about self
- GABA - inhibit action potential at CNS
- Glutamate - enhance action potential at CNS, for learning, memory, fish makes more
- Endorphins - reward, pain reduction; exercise to help moderate the pain (runner's high)
- SP - substance P; pain perception, mood
- Dopamine - reward, inhibits prolactin (cocaine will remain in body for 2 years)
- Steps
- Impulse reaches the presynaptic membrane, become permeable to Ca2+
- Ca2+ flows inward - Ca2+ interacting with protein filaments (microfilament) attached to presynaptic membrane and NT sacs (synpatic vesciles) to contract - exocystosis of the presynaptic membrane
- vesicles release ACh into the synaptic cleft
- NT binds to the receptor on postsynaptic membrane, opening channels to Na+ and creating a new impulse (action potential)
- NT enzyme eg. Acetylcholinesterase (AChE) removes the NT (ACh), and channel closes, synaptic transmission ends, and the NT either reabsorbed or not
- only one direction - because of the location of synaptic vesicles
- Synpatic integration - most neurons have elaborate dendritic trees that receive tens of thousands of synaptic inputs; postsynaptic responses are small, require integration of many to depolarize most neurons to action potential threshold
- sump up the excitatory and inhibitory signals
- excitatory signals / NT push the neuron toward action potential, e.g. Noradrenalin
- inhibitory signals / NT push the neuron away from the action potential, e.g. GABA
- the sum of above two determine if signal propagates or not
- ACh can be both inhibitory and excitatory
- Impulse generation
- generally negative charged cells
- Steps
- Resting potential (phone on) - Na+/K+ pump - 3 Na+ out 2 K+ in, lose the charge, to remain negatively charged, at -70mV; Na+ channel, K+ channel remain closed
- ATP required; actively pumping Na+ out of axoplasm; to maintain greater concentration of Na outside the axon
- Depolarization - if threshold (all-or-none) met at -50mV - strong-enough stimulus opens Na+ channels, Na+ flow inward
- simplified here as bell curve
- Action potential - incoming flood of Na+ during action potential upswing from -65mV to +40mV, passive
- Repolarization - Na+ blocked, and K+ channel open and flow outward during the action downswing -75mV
- meanwhile start the depolarization of the step domino B spread to region B, quickly; while domino C is still at resting state - like riding the roller coaster
- Recovery - refractory peiord, a return to the resting state; the time taken to reset to resting potential after action potential, when the neuron cannot respond to another stimulus due to increased potassium permeability
- a brief time when a neuron is unable to conduct an impulse; also prevents the backflow of action potential
- recycle like magical domino recovers on its own
- movement of Na and then movement of K
- When neuron at rest, Na more concentrated outside the cell; and K more concentrated inside the cell; cell negative charged
- Glia - glial cells (supporting cells, non-neuronal cells), 4 fx, one of it
- Myelin sheath - support cells, surround the axon fo a neuron, composed of fat, increase impulse propagation
- Schwann cells (one of glia at PNS VS neuroglial cells at CNS) covers the axon blocking the movement of Na+/K+
- forcing the wave of depolarization to jump from node to node (blocking intervening gateways), speeding up the impulse flow
- saltatory (table; to hop, skip) conduction
- voltage push; current quantity
- without 5m/s, with myelin - 120-200m/s
- Nodes of Ranvier - gaps between schwann cell, depolarized region; where you can find the sodium gates
- Brain
- Cerebellum - little brain, stand on your one foot; coordinate voluntary movement, muscular activities and maintains equilibrium
- Cerebrum - brain, primary association centre of brain, memory; process sensory input and coordinate motor responses; consciousness
- Thalamus - switch board; sort, filter and passes sensory info (impulses) to all parts of the brain
- synthesia, hear color; color of the music
- central relay station for sensory impulses
- Hypothalamus - autonomic control centre on thirst, hunger, sleep, body temperature; metabolic ra; integrated control of the endocrine gland and hormones, e.g. ADH (water regulation), GnRH (reproduction, testosterone, estrogen)
- Pituitary
- Corpus callosum - nerve tract joing the left and right hemispheres of Cerebrum
- cross-wired: left-right; allows the sharing of sensory information from both sides of the body
- Brain stem - posterior stalk-like part of the brain connecting cerebrum with spinal cord
- Medulla oblongata - vital fx, heart rate, respiration, and blood pressure; regulate reflexes on swallowing, coughing, sneeze, hiccup, vomit
- Pons - regulates respiration, connect cerebellum to cerebrum
- Midbrain
- Meninges - layers of tissue surrounding the brain and spinal cord; protecting the CNS; sheath of the brain: layers - pia, arachnoid, dura mater;
- Lobes - phineas gage
- Occipital - vision (not all, but mostly, like pictures seen)
- back of the skull; slightly larger in women (have a wilder field of view; see more shades of color)
- Parietal - sensation of temperature, pain, touch (pressure on surface); understanding speech (language centre, but not all)
- Temporal - sense of smell and hearing
- Frontal - problem solving and motor control; mind; sense of aesthetics
- Pareidolia - the tendency to perceive a specific, often meaningful image in a random or ambiguous visual pattern
- Amygdala - where alcohol may travel to directly or through frontal, and people can get aggressive thereby
- Neuroendocrine
- TSH stimulates the release of T4 from thyroid gland which regulate oxidative metabolism as body's gas pedal
- high temperature detected by Hypothalamus and decrease releasing hormone (and cause sweat, thirst, flushing; if low temp - shiver, hunger, cyanosis, blood pool in the core) to Anterior pituitary) to decrease TSH
- Test
- synaptic ending of (sensory) neurons
Kaplan
MeSH
- Central Nervous System [A08.186]
- Ganglia [A08.340]
- Nerve Net [A08.511]
- Neural Pathways [A08.612]
- Neuroglia [A08.637]
- Neurons [A08.675]
- Neurosecretory Systems [A08.713]
- Peripheral Nervous System [A08.800]
- Synapses [A08.850]