Chapter 2 - Nervous System Organization Flashcards
What are the four common features of neurons? What is the function?
- cell body
- dendrites
- axon
- terminal synaptic buttons
What is the function of neuron?
- receive and conduct electrochemical signals
Cell body of neuron
metabolic center, protein synthesis, DNA located in nucleus
Dendrites
receive info from other cells
Axon
- info/AP is conducted down this to other neurons, muscles or glands
- surrounded by myelin sheaths
Terminal synaptic buttons
- chemical communication w/ other neurons
- main proponent in the release of neurotransmitters
- contain vesicles w/ NTs
Myelin sheath
covers the axon of some neurons and helps speed of impulses
Nodes of Ranvier
gaps btwn myelin
Microglia
- glial cell in CNS
- phagocytic, clean/metabolize debris and dead cells
- increase in number when brain is injured
Astrocytes
- glial cell in CNS
- feet form BBB, provide nutrient (glucose) and structural support, also phagocytic
Oligodendrocytes
- glial cell in CNS
- form myelin sheaths
Schwann cells
- glial cell in the PNS
- form myelin sheaths
Resting membrane potential
- -70 mV
- caused by electrical imbalance btwn inner and outer surface of membrane
What ions maintain resting membrane potential?
- Na+ - outside of membrane, always excitatory
- Cl- - outside of membrane, always inhibitory
- K+ - inside of membrane, always inhibitory
- negatively charged proteins
Action potential
- electrical potential across neuron membrane that raises potential to threshold (-55mV)
What do action potentials result in?
- selectively permeable membrane to ions
- active transport of Na+ and K+
- voltage gated Na+ channels open, letting Na+ go into cell, triggers opening of K+ channels, which moves K+ out of the cell
Channel
- ions can cross the lipid belayed through the appropriately shaped channel
Gated channel
- changes shape to allow certain substances to cross membrane
- voltage and chemically gated
Pump
- changes shape to carry substances across the membrane
Depolarization
- when the membrane is getting less negative
- typically results in reaching threshold
Absolute refractory period
NO action potential can occur
Relative refractory period
requires a higher depolarization in order to reach threshold
Where do neurons communicate?
at the synapse
- NTs are released
What occurs when neurons communicate?
- rupture of vesicles that release NTs into the synaptic cleft
- NT binds to binding site and causes the pore to open on the postsynaptic cell
Excitatory Post Synaptic Potential (EPSP)
- more likely to cause an AP by depolarizing the membrane
Inhibitory Post Synaptic Potential (IPSP)
- repolarizes the membrane, making it less likely to cause an AP
Acetylcholine
- motor control, autonomic nervous system (parasym), memory, sleep/wake
- located at neuromuscular junction
Norepinephrine
- mood!, hormones, arousal, attention, and eating
Serotonin
- sleep/wake cycle, appetite, mood!
Dopamine
- motor behavior!, pleasure/reward!, cognition
Glutamate
- major excitatory NT in the brain
- more likely to cause APs, depol. the cell
GABA
- major inhibitory NT in the brain
- more likely to inhibit APs, repol. the cell
Agonist
- mimics NT closely enough to activate receptor
- EX: morphine mimics endorphines
Antagonist
- blocks NT by occupying the receptor site
- EX: curare blocks ACh receptors
Central Nervous System (CNS)
- mediates behavior
- brain and spinal cord
Somatic Nervous System
- transmits sensation and produces movement
- cranial nerves and spinal nerves
Autonomic Nervous System
- balances internal functions
- sympathetic - fight or flight (arousing)
- parasympathetic - rest and digest (calming)
What protects the brain?
- Skull - uneven thickness and bony projections to hold brain in place
- Meninges - Dura mater (tough), Arachnoid membrane (subarachnoid space contains CSF and blood), Pia mater (directly on brain, meningitis occurs here)
Ventricular system
- produces and houses CSF, provides buoyancy and cushioning to brain, and allows for disposal of waste
- blockage results in buildup of pressure
- R lat., L lat., third and fourth
Circle of Willis
- communicating arteries provide blood btwn front and back of brain
- provides protection in that if carotids are tied off, blood flow is not completely blocked in brain
- middle cerebral artery supplies blood to motor areas
What is the brainstem composed of?
- pons - arousal/sleep/wake
- medulla - BP, respirations, HR
What is the reticular activating system?
- pons and medulla functioning together
- imp. for selective attention
- overactivation results in sensory deprivation
- damage could result in coma
Hypothalamus
- works closely w/ pituitary gland
- release of hormones, metabolic function, homeostasis, body temp
- stimulates adrenal gland during stress response
Thalamus
- all sensory info other than smell is processed here then sent to designated lobe
Basal Ganglia
- higher motor function (initiating and planning movements)!!
- cognition and mental flexibility controlled by caudate nucleus
- communicated w/ the cerebellum and red nucleus
Limbic System
- motivation and emotional regulation
- amygdala - fear, emotional memory/conditioning
- hippocampus - learning and (spatial) memory, spatial navigation
Corpus Callosum
- large bundle of fibers that allows simultaneous communication btwn R and L hemispheres
- anterior commissure and hippocampal commissure also contribute to function
Clive Wearing
- herpes caused damage to hippocampus
- experiences amnesia and mood swings/early bouts of aggression
- auditory hallucinations
- 20 second bouts of memory
Cerebellum
balance and coordination
