Nervous System

What is the function of the nervous system?

• our body is regularly exposed to stimuli, which push it out of its steady state (homeostasis)

• the nervous system senses theses changes and coordinates the responses to restore homeostasis

What are the main parts of the nervous system?

• brain

• spinal cord

• nerves that branch from each

In what ways is the nervous system organized?

• central nervous system (CNS)

• peripheral nervous system (PNS)

Where is the central nervous system found?

• along the midline

What main parts does the central nervous system contain?

• the brain

• the spinal cord

What is the function of the central nervous system?

• to process the information sent from other parts of the nervous system and coordinate appropriate responses

Where is the peripheral nervous system located?

• branches from CNS towards the sides of the body

What are the main parts of the peripheral nervous system?

• nerves

What is the function of the peripheral nervous system?

• to carry information to and from the CNS

What are the types of pathways of the PNS?

• sensory

• motor

What is the function of sensory pathways?

• carry information from receptors to the CNS

What are the types of receptors?

• mechanoreceptors

• chemoreceptors

• photoreceptors

• nociceptors

• thermoreceptors

What sense do mechanoreceptors pick up?

• hearing

• touch

What sense do chemoreceptors pick up?

• smell

• taste

• pH

What sense do photoreceptors pick up?

• vision

What sense do nociceptors pick up?

• pain

What sense do thermoreceptors pick up?

• temperature

What is the function of the motor pathways?

• carry information from the CNS to effectors to carry out the response

What are the types of effectors?

• muscles

• glands

What are the types of nervous systems found in the motor pathways?

• somatic

• autonomic

Is the somatic nervous system voluntary or involuntary?

• voluntary

What is the somatic nervous system connected to?

• skeletal muscle

Is the autonomic nervous system voluntary or involuntary?

• involuntary

What is the autonomic nervous system connected to?

• smooth muscle

• cardiac muscle

• glands

What are the types of autonomic nervous systems?

• sympathetic

• parasympathetic

What is the function of the sympathetic nervous system?

• speeds up bodily procession by regulating stress response (fight/flight/freeze)

What is the function of the parasympathetic nervous system?

• regulates rest and digestion

What does the sympathetic nervous system do in the body?

• dilates pupils

• inhibits salivation

• relaxes bronchi

• accelerates heartbeat

• inhibits peristalsis and secretion

• stimulates glucose production and release

• secretion of adrenaline and noradrenaline

• inhibits bladder contraction

• stimulates orgasm

What does the parasympathetic nervous system do in the body?

• constricts pupils

• stimulates saliva flow

• constricts bronchi

• slows heartbeat

• stimulates peristalsis and secretion

• stimulates bile release

• contracts bladder

What is the neuron?

• basic structural and functional unit of the nervous system that:

  • responds to chemical and physical stimuli

  • conducts electrochemical signals

  • releases chemicals to regulate various body processes

What are the parts of the neuron?

• dendrite

• cell body (soma)

• axon

• terminal bulbs

• myelin sheath

• node of Ranvier

What are dendrites?

• short branching arms that receive signals from sensory receptors or other neurons

What is the cell body (soma)?

• contains the nucleus

• site of metabolism

• processes information

What is the function of the axon?

• conducts impulses away from the cell body and towards other neurons or effectors

Where are terminal bulbs located?

• at the end of axons

What is the function of the terminal bulbs?

• contain and release neurotransmitters

What are neurotransmitters?

• chemical messengers that cross the gap between neurons (the synapse) or between neurons and receptors or effectors

What is the myelin sheath (structure)?

• a fatty, insulating layer which encloses the axons of some neurons

What is the function of the myelin sheath?

• to allow neurons to transmit signals faster

What do neurons with a myelin sheath look like vs without a myelin sheath?

• with: white appearance

• without: grey appearance

What is the node of Ranvier?

• gap in the myelin sheath through which the nerve impulse “jumps” to speed up transmission

What is the sensory neuron (function)?

• gather information from receptors and pass it to the CNS

• take sensory information rom the environment (i.e. getting poked with a needle) and sends the signal to the brain

What is the sensory neuron (structure)?

• cell body is to the side of the axon to allow the signal to bypass the processing area, so that a response can be more rapid?

Where are interneurons located?

• the CNS

What is the function of interneurons?

• process and integrate information so that a response can be generated

• make up a majority of neurons in the body

• the “middle man”, transmitting information between sensory and motor neurons

• play a key role in memory, learning, and planning

What is the function of motor neurons?

• pass information from the CNS to effectors

• communicate information from the brain to tissues and organs throughout the body, allowing for movement

What is a nerve?

• a collection of neurons to form a tissue

What is the structure of a motor neuron?

• cell body is located to the top of the neuron (across from synaptic end bulbs)

What it’s he structure of an interneuron?

• cell body is located in the middle

What are the glial cells?

• satellite cells

• Schwann cells

• oligodendrocytes

• astrocytes

• microglia

• ependymal cells

What are the glial cells that are found in the PNS?

• satellite cells

• Schwann cells

What are the glial cells that are found in the CNS?

• oligodendrocytes

• astrocytes

• microglia

• ependymal cells

What is the function of satellite cells?

• regulate the environment surrounding neurons

What is the function of Schwann cells?

• produce myelin sheath for one neuron

What is the function of oligodendrocytes?

• produce myelin sheath for multiple neurons

What is the function of astrocytes?

• regulate the environment in the brain by forming the blood-brain barrier

What is the function of microglia?

• immune cells that protect the brain against injury and disease

What is the function of ependymal cells?

• create and circulate cerebrospinal fluid

What is the electrical impulse?

• the signal that travels down a neuron to convey information

How is the electrical impulse started?

• caused by a voltage differential between the inside and outside of the neuron

How is the voltage differential created?

• by two forces as ions move across the membrane:

  • diffusion along the concentration gradient

  • electrical attractions

What is resting potential?

• when the neuron is not firing (sending a signal)

• during rest, the transport mechanisms make the neuron positive outside and negative inside

What is the average differential?

• -70 mV

What is the first step to establishing resting membrane potential?

• the cell makes organic anions (-), mostly proteins, that are too large to diffuse out of the cell

• negative charge builds inside

What is the second step to establishing resting membrane potential?

• the sodium-potassium pumps are integral proteins which use active transport to move 3 Na+ out and 2K+ in

• Na+ builds up outside of the cell and wants to diffuse back in

• K+ build up inside of the cell and wants to diffuse out

What is the third step to establishing resting membrane potential?

• voltage-gated leak channels are integral proteins that act as doors which allow ions to move across the membrane by diffusion

• at rest, K+ channels are open, Na+ channels are closed

• K+ leaves the cell along their concentration gradient

What is the fourth step to establishing resting membrane potential?

• Cl- will be pumped out of the cell via active transport to help attract the positive ions outwards