central nervous system (cns)speedwaybiology.weebly.com/.../ap_biology_-_chapters_48_and_49_p… ·...

Central nervous system (CNS) = brain + spinal cord Peripheral nervous system (PNS) = nerves

throughout body

Sensory receptors: collect info

Sensory neurons: body brain/SC

Motor neurons: brain/SC body (muscles, glands)

Interneurons: connect sensory & motor neurons Nerves = bundles of neurons

Contains motor neurons +/or sensory neurons

Peripheral nervous system

Somatic nervous system

Autonomic nervous system

Sympathetic division

Parasympathetic division

Enteric division

cell body: nucleus, organelles dendrites: receive incoming messages axons: transmit messages to other cells myelin sheath: insulates axon, speeds up nerve impulses synapse: junction between 2 neurons neurotransmitter: chemical messengers sent across

synapse

Eg. acetylcholine, dopamine, serotonin glia (glial): support cells

Astrocytes, oligodendrocytes (forms CNS myelin sheath), Schwann cells (forms PNS myelin sheath)

Microelectrode

Reference electrode

Voltage recorder

–70 mV

A Na+/K+ pump maintains a negative potential inside the neuron.

Resting potential: membrane potential at rest

Voltage-gated Na+ channel = closed High Na+ outside / High K+ inside cell Nerve impulse: change in membrane potential =

action potential

Action potential – neuron membrane depolarizes and causes all-or-nothing response

Voltage-gated

Na+ channels

open

Na+ enters cell K+ channels

open K+ leaves cell

Conduction of an action

potential

Saltatory conduction speed: 120 m/sec

Released by presynaptic membrane into the synaptic cleft

Bind to receptors on postsynaptic membrane, then broken down by enzymes or taken back up into surrounding cells

Types of neurotransmitters:

Excitatory: speed up impulses by causing depolarization of postsynaptic membrane

Inhibitory: slow impulses by causing hyperpolarization of postsynaptic membrane

Acetylcholine: very common neurotransmitter, can be excitatory or inhibitory

Other common neurotransmitters: epinephrine, norepinephrine, dopamine, serotonin

Nicotine: mimics acetylcholine – speeds heart rate LSD/mescaline – bind to serotonin and dopamine

receptors hallucinations Prozac – enhances effect of serotonin by inhibiting

uptake after release Morphine, heroin – bind to endorphin receptors

decrease pain perception Viagra – increase NO (nitric oxide) effects maintain

erection Parkinson’s Disease – lack of dopamine Alzheimer’s Disease (AD) – develop senile plaques,

shrinkage of brain tissue

Simple, automatic response to a stimulus Conscious thought not required Stimulus detected by receptor sensory

neuron interneuron (spinal cord) motor neuron cause effector (muscle or gland cell) to respond

Gray matter

White

matter

Ventricles

Structure Function

Brainstem *Oldest evolutionary part* Medulla oblongata – control breathing, circulatory

Cerebellum Motor, perception, cognitive functions

Thalamus Main center for sensory info

Hypothalamus Homeostasis (body temp, appetite, thirst, circadian rhythm, hormones), basic survival behaviors

Cerebrum Information processing (thinking, memory, personality, interpretation of sensory input)

Corpus callosum Connect hemispheres