Hap Lec - Nervous System Structure and Functions

Nervous System

Complex system of neurons and neuroglia.

2 kg (4.5 lb)

How much mass does nervous system have in the body? which amounts to 3% of total body weight

CNS, PNS

2 main subdivisions of the nervous system.

Central Nervous System (CNS)

Includes brain and spinal cord.

Peripheral Nervous System (PNS)

Nervous tissue outside the CNS.

nerves (cranial & spinal)
ganglia
enteric plexuses
sensory receptors

components of PNS

Autonomic Nervous System

system under PNS that involves the Involuntary control of smooth, cardiac muscles, and glands.

ANS

consists of sensory neurons within nerves that convey info from autonomic sensory receptors located in visceral organs such as stomach and lungs to the CNS and motor neurons that conduct nerve impulses from CNS to smooth and cardiac muscle and glands.

Sympathetic, Parasympathetic

2 main branches of the motor part of the ANS

Somatic Nervous System

Voluntary control of skeletal muscles.

Somatic Nervous System

consists of sensory neurons that convey info from somatic receptors in the head, body wall, and limbs from receptors for special senses to the CNS and motor neurons that conduct impulses from CNS to skeletal muscles only.

stomach, lungs

where are the autonomic sensory receptors primarily located?

Sensory Division

Conducts action potentials from sensory receptors to CNS.

impulses

other word for action potentials

afferent division

other term for sensory division

efferent division

other term for motor division

Motor Division

Conducts impulses from CNS to effector organs like muscles and glands.

Sensory Neurons

Transmit impulses from receptors to CNS.

Motor Neurons

Transmit impulses from CNS to muscles or glands.

Interneurons

Connect sensory and motor neurons in CNS.

Receive sensory input
Integrate information
Motor Function (Control muscles and glands)
Maintain homeostasis
Establish and maintain mental activity

functions of the Nervous System

Neurons, Neuroglia

cells of the nervous system

nerve cells

other term for neurons

neurons

receives stimuli, conduct action potentials, and transmit signals to other neurons or effector organs

neurons

cell under the nervous system that DOES NOT undergo cell division

neurons

responsible for the reception of stimuli and transmission of impulses

Neurons

Cells that transmit signals in the nervous system.

Cell body/Soma
Dendrites
Axon

3 parts of a neuron

Cell body/Soma

the part of a neuron that coordinates information-processing tasks and keeps the cell alive, contains the nucleus

dendrites

short, often highly branching cytoplasmic extensions that are tapered from their bases at the neuron cell body/soma

dendrites

usually receives information from other neurons or from sensory receptors and transmit the info TOWARD the neuron cell body

Axon

long, slender projection of a nerve cell/neuron

Axon

typically conducts electrical impulses AWAY from the neuron's cell body/soma

Pseudo-unipolar
Bipolar
Multipolar

3 types of neurons based on number of protoplasmic processes

Pseudo-unipolar

with only one protoplasmic process that divides into two processes a short distance from the cell body. One extends from periphery and other extend to CNS

dorsal root ganglion of the spinal cord

where are pseudo-unipolar neurons found?

bipolar neuron

type of neuron with 2 protoplasmic processes (axons and dendrites)

retina of the ere and in nasal cavity

where are bipolar neurons found?

Multipolar neuron

type of neuron with several dendrites and one axon

within CNS, including all motor neurons

where are multipolar neurons found?

sensory neuron

type of neuron that transmit impulses from sensory receptor to CNS and is UNIPOLAR

motor neuron

type of neuron that transmit impulses from CNS to effector organs and is MULTIPOLAR

Adjustor/Interneuron

type of neuron that connects sensory and motor neuron located in the nerve center and is MULTIPOLAR

Node of Ranvier

a gap in the myelin sheath of a nerve, between adjacent Schwann cells. also called neurofibril node

Neuroglia

nonneuronal cells of the CNS and PNS.

neuroglia

supporting cells for the nourishment, protection, and insulation of neurons

neuroglia

cell of the nervous system that UNDERGOES cell division thus may cause brain tumor

Astrocytes

Star-shaped neuroglia located between neurons and capillaries

astrocytes

type of neuroglia that is the major supporting tissue in the CNS

astrocytes

type of neuroglia that contributes with the blood brain barrier (BBB)

Microglia

type of neuroglia that acts as the Immune cells protecting CNS from infection.

microglia

type of neuroglia that helps protect the brain by removing bacteria and cell debris (phagocytes)

Ependymal Cells

type of neuroglia that line the fluid-filled cavities (ventricles) of the CNS cavities

Ependymal Cells

type of neuroglia that form choroid plexus to produce cerebrospinal fluid (CSF) and also help move CSF through CNS through cilia

Oligodendrocytes

type of neuroglia that forms Myelin sheaths around the axons or enclosed unmyelinated axons in the CNS.

Schwann Cells

type of neuroglia that forms myelin sheaths around axons or enclosed unmyelinated axons in the PNS.

oligodendrocytes

type of neuroglia that is able to myelinate multiple axons even with it being only one

Schwann cells

type of neuroglia that can only myelinate a single axon

schwann cells

type of neuroglia that allows for axonal growth and regeneration

oligodendrocytes

type of neuroglia that inhibits axon growth and regenration

Myelin Sheath

Insulating layer around axons. it prevents almost all electrical current flow through the cell membrane

myelin sheath

specialized sheath wrapped around the axons of neurons within the CNS and PNS

Gray Matter

Contains groups of neuron cell bodies and dendrites.

cortex

In the CNS, gray matter on the surface of the brain is called the

ganglion

In the PNS, a cluster of neuron cell bodies is called a

White Matter

consists of Bundles of parallel myelinated axons which are whitish in color

nerve tracts/conduction pathways

In the CNS, white mattter forms

nerves

In the PNS, bundles of axons and their connective tissue sheaths are called

Resting Membrane Potential

Uneven charge distribution in resting cell membrane making the inside of the cell membrane negatively charged compared to outside

Depolarization

Na+ influx makes cell membrane positively charged.

Repolarization

K+ efflux restores negative membrane charge.

Leak and gated-ion channels

two types of open ion channels causing difference in membrane permeability

Chemically gated channels

type of gated-ion channel that is opened by neurotransmitters or other chemicals

voltage-gated channels

type of gated-ion channel that is opened by change in membrane potential

Action Potential

A rapid change in the membrane potential of an excitable cell

action potential

the rapid depolarization and repolarization of the cell membrane

T

T or F
muscles and nerve cells are excitable cells meaning that the resting membrane potential changes in response to stimuli that activate gated ion channels

Leak Channels

Ion channels allowing passive ion flow.

Gated-Ion Channels

Ion channels that open in response to stimuli.

Chemically Gated Channels

Open when neurotransmitters bind.

Voltage-Gated Channels

Open due to changes in membrane potential.

Cerebrospinal Fluid (CSF)

Fluid that cushions and nourishes the brain.

Local Potentials

Changes in membrane potential due to stimulation.

All-or-None Principle

Action potential occurs if threshold is reached. No action potential occurs if threshold is not reached

Unmyelinated Axons

Slowly conducts action potentials via continuous conduction.

Myelinated Axons

Rapidly Conducts action potentials via saltatory conduction.

continuous conduction

action potential is conducted along the entire axon cell membrane

saltatory conduction

action potentials "jump" from one node of ranvier to the next along the length of axon

Synapse

Junction where the axon of one neuron interacts with another neuron or with an effector organ

Presynaptic Terminal

End of the axon releasing neurotransmitters.

Postsynaptic Membrane

Membrane of the dendrite or effector cell

Synaptic Cleft

Space separating the presynaptic and postsynaptic membranes.

Calcium Ions (Ca+)

Trigger neurotransmitter, acetylcholine (Ach) release at presynaptic terminal.

Acetylcholine (Ach)

Neurotransmitter released into the synaptic cleft.

T

T or F
When Na+ diffuses down their concentration gradient the muscle fiber membrane is depolarized.

presynaptic terminal

An action potential arrives at the __________ _________, causing Ca+ channels to open

Na+

Diffusion of Ach across the synaptic cleft and binding of Ach to Ach receptors on the postsynaptic muscle fiver membrane opens the ______ channels

Reflex

An involuntary reaction in response to a peripheral stimulus.

reflex

allows a person to react to a stimuli more quickly than if conscious though was involved

spinal cord, brainstem

most reflexes occur in the _______ ______ or ________ rather than in the higher brain centers