Bio Exam 2

CNS

Brain, spinal cord (interneurons)

PNS

Afferent/efferent neurons

Afferent neurons

sensory neurons that pick up and send signals away

Does not have dendrites protruding from cell body

Peripheral branch

Branch on axon from cell body to periphery

Central branch

Branch on axon from cell body to spinal cord

Glial cells/Neuroglia

Non-neuronal cells that provide nutrion and support to neurons

Ependymal cells

Type of glial cells that produce cerebrospinal fluid in CNS

Microglia

Type of glial cells cells that ingest and break down pathogens

In CNS

Astrocytes

In CNS

Cover surfaces of blood vessels for structural support

Help maintain ion concentrations in interstitial fliod surrounding them

Satellite cells

In PNS

Cover surfaces of blood vessels for structural support

Help maintain ion concentrations in interstitial fliod surrounding them

Schwann cells

In PNS

Form myelin sheath

Oligodendrocytes

In CNS

Form myelin cheath

White matter

Myelinated axons, glial cells

Grey matter

Neuronal cell body

Dorsal root

Afferent

Ventral root

Efferent

Synapse

Junction between axon terminals of a neuron and the receiving cell (another neuron, muscle fiber, gland cell)

Axosomatic

Type of synapse between presynaptic terminal and Soma

Axoaxonic

Type of synapse between axons of presynaptic cells and postsynaptic cells

Axodendritic

Type of synapse where the axon terminal ends on a dendrite spine

Presynaptic

Transmitting

Postsynaptic

Receiving

Node of Ranvier

Gaps in myelin that expose axon membrane directly to extracellular fluid

Node of Ranvier function

Increase speed at which electrical impulses move along axons because they “jump” from node to node via saltatory conduction

Way of processing info in nervous system

1. Sense

2. Integrate

3. Act

Dendrites

Branches that act as primary input site for neuron

Cell body

Contains nucleus of neuron

Axon

Fiber extending from cell body and transmits electrical signals to other cells

Myelin sheath

Fatty protein-layer that wraps around axon to provide protection and speed up electrical signal transmission

Axon terminal

Distal end of axon where signal is transmitted to other neuron cells/effector cells

Electrical synapse

Found in heart muscle tissue and some smooth muscle

Chemical synapses

Utilize neurotransmitters

Membrane potential

Difference in electrical charge on two sides of membrane

Electrochemical gradient

Net driving force on ion

Unipolar

Sensory neurons with cell bodies located in spinal/craniel nerve ganglia

Bipolar

Found in olfactory epithelium, retina of eye, and ganglia of vestibulocochlear nerve

Multipolar

Most common type of neuron, located in the central nervous system (brain and spinal cord). Multipolar neurons have more than two processes emanating from the neuron cell body

Pseudounipolar

unipolar neurons that embryologically originate as bipolar neurons and subsequently become unipolar.

Equilibrium Potential

Membrane potential at which voltage gradient of a particular ion balances the concentration gradient for each ion

Action potential

Abrupt and transient change in membrane potential that occurs when neuron conducts an electrical impulse

Nerve nets

Loose mesh of neurons found in radially symmetrical animals

Nerve cord

Bundle of nuerves which extend from central ganglia to rest of body

Ganglia

Functional clusters of neurons

Bilateral symmetry

Body parts are mirror images on either side of midle; useful bc paired nerves link brain lobes with specific muslces/receptors to allow for sophisticated sensory processing

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Blood Brain Barrier

Separation of circulating blood and CSF; prevents harmful things from coming in

Occurs along all capillaries and consists of tight junctions that prevent things from coming in

Cerebrospinal Fluid (CSF)

Clear, colorless fluid produced in choroid plexus (a complex of glial cells called ependymal cells)

CSF found in

Brain/spinal cord

CSF does two things:

• Circulates nutrients and chemicals filtered from the blood

• Removes waste products from the brain

CSF Function

Provides buoyancy and support to brain (brain floats in CSF bc they’re similar in density) so nervous tissue doesnt die by scraping/hitting cranium

Ventricular system

Cavities in brain filled with CSF

Four ventricles

Two lateral ventricles, third ventricle, fourth ventricle

Ventricles function

Produce, transport, and remove CSF

Meninges

Layers of connective tissue (membranes) covering brain and spinal cord

3 connective tissue layers

1. Pia

2. Arachnoid

3. Dura mater

Function of Meninges

• Provide structural support for blood vessels

• Serve as “pad” between brain/skull

Forebrain

Forms cerebrum (left/right hemispheres)

Main parts of forebrain

Telencephalon

Diencephalon

Parts of diencephalon

Thalamus and hypothalamus

Left cerebral hemisphere

Focus on details (ex: facial recognition), spoken/written language, abstract reasoning, math

Wernicke’s and Broca’s areas

Right cerebral hemisphere

Focus on broad background, intuitive thinking, conceptualization, arts, etc.

Cerebral Cortex

Outermost thin layer of gray matter (in mammals, comprised of 6 layers of neurons, 2-4mm thick in humans), covering a core of white matter

Folds to increase surface area

Grey matter

neuron cell bodies and dendrites

White matter

axons (many axons have myelin sheaths)

Primary somatosensory area

Receive and integrate sensory info

Located in parietal lobes of each hemisphere

Integrates info regarding touch/pressure, temperature, pain

Primary motor area

Planning, control, and execution of voluntary movements

Association areas

Integrate sensory info, formulate responses, relay responses to motor area

Frontal lobe

Executive function (thinking, organization, planning, problem solving, etc.)

Temporal lobe

Smell, sound, memories

Parietal lobe

Perception/integration of stimuli

Occipital lobe

Vision

Cerebellum

Coordinates/refines body movements/position and compares sensory input with signals from cerebrum that control voluntary body movement

Brain stem components

Medulla oblongata, pons, midbrain

Brain stem function

Connects brain to spinal cord

Midbrain

Smallest region of brain

Contains VTA

Ventral Tegmental Area (VTA)

Dopamine/serotonin produced neurons

Involved pleasure pathway/reward circuit

Substantia nigra

Part of midbrain involved in control of body movement

Reticular formation

Network of neurons in brain stem

Ascending divison

Sends signals to thalamus to activate cerebral cortex

Descending division

Receives info from hypothalamus

Connects with interneurons of spinal cord that control skeletal muscle contraction

Thalamus

Structure between cerebral cortex and midbrain

Relays signals from special senses and motor signals to cerebral cortex

Hypothalamus

Limbic System Components

Parts of thalamus, hypothalamus, basal nuclei

Amygdala

Hippocampus

Olfactory bulbs

Amygdala

Emotion, fear

Hippocampus

Memory

Olfactory bulbs

Smell

VTA

Releases dopamine

Nucleus Accumbens

Contains dopamine sensitive cells (feels of pleasure)

Amygdala/Hippocampus

Role in memory and whether experience is desirable

Prefrontal cortex

Coordinates all information and determines behavior

PNS

31 pairs of spinal nerves

Connects CNS and limbs/organs

Divided into afferent/efferent systems

PNS Divisions

Somatic/Autonomic

Somatic

Mostly voluntary/conscious movements

Autonomic nervous system

Functions below level of consciousness (involuntary)

Divisions of autonomic nervous system

Sympathetic

Parasympathetic

Sympathetic

Fight/Flight causes increase in:

• force/rate of heartbeat

• Increase in BP

• Suppress activities such as digestion

Parasympathetic

Used for housekeeping functions during low stress time

Vagus nerve

Extends below head, neck, chest, and abdomen

Vagus nerve function

Contributes to innervation of viscera/organs

Conveys sensory info about state of body’s organs to CNS

80-90% of nerve fibers in vagus nerve are afferent nerves

Vasovagal Syncope

Vagus nerve overreacts to a trigger and causes syncope