Unit 15: Nervous System🧠

What 2 structures does the nervous system include?

1. brain

2. spinal cord

What makes the nervous system, unlike systems such as the digestive system, where organs like the stomach, esophagus, and liver are visibly distinct, diffrent?

many parts of the nervous system are less obviously separated

Many nervous system regions look ____ and must be distinguished using tools such as microscopy or electrophysiology

similar

What are the 2 major regions of the nervous system called?

1. central nervous system (CNS)

2. peripheral nervous system (PNS)

What is included in the central nervous system (CNS)?

brain and spinal cord

What is included in the peripheral nervous system (PNS)?

everything else

The brain is located in the ____ cavity, and the spinal cord is located in the ____ cavity

cranial, vertebral

What are the 2 main types of cells in nervous tissue?

1. neurons

2. glial cells

What is the function of glial cells?

support neurons

What is the function of neurons?

communication

A neuron has a ____ (cell body) and extensions called ____

soma, processes

What is an axon?

the process that connects a neuron to its target, and carries signals away from the cell body

What are dendrites?

branching processes that extend from the soma and receive information

What are the 2 main cell types of the peripheral nervous system (PNS)?

1. nerves

2. ganglia

____ structures are not as visibly distinct from the outside and are best identified by examining nervous tissue under a ____

CNS, microscope

What is a nerve?

bundle of axons in the PNS

What is ganglia?

collection of neuron cell bodies in the PNS

How do dendrites receive most of their input?

from other neurons

Grey matter regions contain what?

cell bodies and dendrites

White matter regions contain what?

axons

Why does white matter appear white?

because axons are insulated by myelin

What is myelin?

a lipid-rich substance

Grey matter is not always literally grey; it can appear ____ because of ____ or tan depending on how long the tissue has been ____

pinkish, blood, preserved

Grey matter may look grey partly because it is ____ than the surrounding white matter

darker

The distinction between grey and white matter is used mainly for the ____, where large regions can often be seen without a microscope

CNS

What type of matter makes up the outer cortex of the brain?

grey matter

A localized collection of neuron ____ ____ has different names depending on its _____

cell bodies, location

____ = a collection of neuron cell bodies in the CNS

____ = a collection of neuron cell bodies in the PNS

nucleus, ganglion

The word nucleus has what 3 meanings?

1. the center of an atom

2. the part of a cell containing DNA

3. a functional center containing neuron cell bodies in the CNS

What is a group of nuclei in the CNS called?

basal ganglia

A bundle of axons has different names depending on where it is ____

located

____ = bundle of axons in the CNS

____ = bundle of axons in the PNS

tract, nerve

Optic ____ = axons from the eye in the PNS

Optic ____ = boundary between PNS and CNS

Optic ____ = same axons after entering the CNS

nerve, chiasm, tract

What are the 3 basic functions of the nervous system called?

1. sensation

2. integration

3. response

What is sensation in the nervous system?

receiving information about the environment through afferent (sensory) information

What is integration in the nervous system?

processing and combining sensory information with memories, learning, emotions, and cognition to decide what to do

What is response in the nervous system?

producing an efferent (motor) response to the information

What are the 2 divisions the nervous system can be divided in how it controls the body?

1. somatic control

2. autonomic control

What is somatic control in the nervous system?

conscious control of skeletal muscles

What is autonomic control in the nervous system?

regulates involuntary functions

The ____ nervous system (ENS) is a division of the ____ involved specifically in gastrointestinal functions

enteric, PNS

A ____ is an event or change in the environment that the nervous system detects

stimulus

The major five senses are:

Taste → ____ stimuli

Smell → ____ stimuli

Touch → ____/____ stimuli

Sight → ____ stimuli

Hearing → ____/____ stimuli

chemical, chemical, physical/mechanical, light, sound/physical

Examples of ____ stimuli include stretch of an organ wall or changes in ion concentration in the blood

internal

Sensory information is sent to the nervous system for ____

integration

Integration determines the appropriate ____

response

Responses can involve ____ or ____

muscles, glands

What muscle tissues can the nervous system control?

all three types

What are the 3 systems that can be activated during a response?

1. somatic nervous system (SNS)

2. autonomic nervous system (ANS)

3. enteric nervous system (ENS)

Somatic nervous system (SNS) → ____ perception + ____ ____ motor responses

conscious, skeletal muscle

Somatic responses CAN be ____, meaning they can happen without conscious decision

reflexes

How can learned motor skills also become automatic/unconscious?

through procedural memory

What is procedural memory?

habit learning

Autonomic nervous system (ANS) → ____ control, mainly to maintain ____

involuntary, homeostasis

What are the 3 things that the autonomic nervous system (ANS) controls?

1. smooth muscle

2. cardiac muscle

3. glands

ENS controls smooth muscle and glands in the ____ system

digestive

Is the ENS part of CNS or PNS?

PNS

The ENS can function independently of the ____

CNS

Why is the ENS sometimes considered part of the autonomic nervous system (ANS)?

because it helps regulate digestion

Neurons are electrically ____ and release ____ ____ to target cells

active, chemical signals

Glial cells may also have roles in ____, but neurons are still considered the main cells responsible for nervous system communication

signaling

What are 3 things neurons help with?

1. sensation

2. movement

3. thought processes

What allows neurons to make many connections with other cells?

its structure and 3D shape

What structure contains the nucleus and most organelles?

soma (cell body)

What are extensions from the cell body called?

processes

What do axons carry and where?

nerve impulses away from the soma to target cells

How many axons are there per neuron?

one

How many target cells can an axon communicate with?

many

What structure receives information from other neurons?

dendrites

Dendrites are usually highly ____

branched

What is the specialized contact point where neurons communicate called?

synapse

What is the order in which information generally flows within the nervous system? (4)

dendrites → soma → axon → target cell

What is the one way flow in information called in the nervous system?

polarity

What is the location called where the axon begins from the cell body?

axon hillock

What is the axon hillock also called?

initial segment

What is the insulating covering around many axons called?

myelin

What is myelin made out of?

glial cells

What are gaps between sections of myelin called?

nodes of ranvier

What is nodes of ranvier important for?

electrical signal transmission

What is the myelinated section between two nodes of ranvier called?

axon segment

What is the branched end of the axon that connects with target cells called?

axon terminal

What are the enlarged ends of axon branches that communicate with the target cell called?

synaptic end bulbs

One major classification of neurons is based on the number of ____ attached to the cell body

processes

What is a neurons processes?

its axon and dendrites

What is a unipolar neuron?

1 process containing both the axon and dendrite

What is a bipolar neuron?

has 2 processes, 1 axon and 1 dendrite

What is a multipolar neuron?

3+ processes, has 1 axon and multiple dendrites

Neuron ____ reflects its polarity

structure

A Purkinje cell is named after the scientist who discovered/described it; found in the ____

cerebellum

A pyramidal cell is a ____ neuron with a pyramid-shaped cell body found in the ____ ____

multipolar, cerebral cortex

An olfactory neuron is named based on its function/group related to the sense of ____

smell

Glia comes from a Greek word meaning ____

glue

What are glial cells that support neurons in the CNS called?

astrocytes

What is the shape of astrocytes?

star-shaped

Astrocytes have many cell extensions/processes that interact with what 3 things?

1. neurons

2. blood vessels

3. pia matter

What is pia matter?

connective tissue covering the CNS

Astrocytes maintain the ____ ____ around neurons

chemical environment

Astrocytes remove excess ____ ____

signaling molecules

Astrocytes respond to tissue ____

damage

Astrocytes help form the ____-____ barrier

blood-brain