Lecture 13- Nervous Tissue

CNS

Associated with the brain and the spinal cord

PNS

Associated with the tissue outside the CNS

control and adjust activity of the body, provide brief and swift responses

Main characteristics of the nervous system

afferent division of the PNS

– Brings sensory information to the CNS
– Begins at the receptors

efferent division of the PNS

– Carries motor commands to muscles and glands
– Ends at the effectors

sensory information, motor commands

The PNS provides ___________ to the CNS and carries ______________ away from the CNS

Neurons

Nerve cells that are responsible for the transfer and processing of information in the nervous system

neuroglia

▪ Supporting cells
▪ Protect the neuron

astrocytes, oligodendrocytes, microglia, ependymal cells

what are the neuroglia of the CNS

astrocytes

-largest and most numerous neuroglia

-make up the blood brain barrier (BBB)

oligodendrocytes

form myelin sheath/form internodes and myelin sheath gaps

white matter

Areas of the CNS with mostly myelinated axons

gray matter

Areas of the CNS without of myelinated axons, mostly composed of cell bodies

microglia

phagocytic neuroglia

ependymal cells

-involved in cerebrospinal fluid (CSF) production
▪ Make up a cellular lining called the ependyma

Satellite cells and schwann cells

neuroglia types found in the PNS

peripheral nerves

in the PNS, Axons are bundled together to form __________

ganglia

The cell bodies in the PNS are clustered in __________

satellite cells

neuroglia that surround cell bodies

schwann cells

neuroglia that surround axons to create myelination

neurolemma

surface of the Schwann cell with the nucleus

axolemma

inner layer of a Schwann cell in direct contact with the axon

nodes (of Ranvier)

areas of axons that are not covered by schwann cells

perikaryon

neuron cytoplasm

neurofilaments or neurotubules

make up the neuron cytoskeleton

nissl bodies

clusters of free ribosomes in a neuron

axon hillock

area where the initial segment connects to the cell body

axoplasm

cytoplasm of the axon

collaterals

branches off the axon

telodendria

ends of the axon and collaterals

axon terminals

ends of the telodendrias

axoplasmic transport

the movement of material between the cell body and the axons

axonic

– Has many processes but cannot differentiate between axons and dendrites
– Found only in the CNS

Bipolar

-The cell body is between the dendrite and axon
– Axons are not myelinated

pseudounipolar

-The cell body is off to one side of the axon

multipolar

- Typically has a single axon and multiple dendrites
– Most common type in the CNS

interoroceptors

monitor internal organ activity

exteroceptors

provide information about the external environment

Proprioceptors

monitor position and movement

sensory neurons

– The axons are afferent fibers
– Sends information from the PNS to the CNS

motor neurons

-The axons are efferent fibers
– Send information from the CNS to the periphery

interneurons

– Located entirely in the CNS
– Situated between the motor and sensory neurons
– Analyze sensory input and coordinate motor output

the axons can, but not cell bodies

can nerves regenerate?

threshold stimulus

the level of stimuli to cause a change in membrane permeability

membrane potential

the uneven distribution of positive and negative ions across the plasma membrane

excitability

The ability to conduct the impulse is known as ____________

myelin sheath, large diameter of axons

what makes impulse speed faster?

synapse

the junction between a neuron and another cell

neuronal pools

Neurons can be organized into smaller organized groups called _______________

divergence

The spread of information from one neuron to several neurons

convergence

information going from several neurons to a single neuron

serial processing

Information going from one neuron to the next in a sequence

parallel process

Several neurons are processing the information at the same time

reverberation

Collateral axons extend back toward the origin of the impulse to cause an enhancement or a continuation of the impulse.

• proprioceptors

Which of the following structures are receptors that monitor the position and movement of skeletal muscles and joints?
• exteroceptors
• interoceptors
• proprioceptors
• neuroeffectors

• afferent division of the peripheral nervous system

Which of the following carries
sensory information to the central
nervous system?
• efferent division of the peripheral nervous system
• afferent division of the peripheral nervous system
• somatic nervous system
• autonomic nervous system

• reverberation

Which of the following organization of neuronal pools operates on a feedback mechanism?
• reverberation
• serial processing
• convergence
• divergence

• Schwann cells

Which cells participate in the repair of damaged nerves in the peripheral nervous system by forming a solid cellular cord that follows the path of the original axon?
• satellite cells
• Schwann cells
• ependymal cells
• oligodendrocytes

• threshold stimulus

Which term describes when a stimulus is sufficient to start an action potential?
• synapse
• excitability
• membrane potential
• threshold stimulus

• chemical synapse

Which type of synapse requires a neurotransmitter to be released at the presynaptic membrane?
• gap junction
• electrical synapse
• chemical synapse
• nonvesicular synapse

• receptor, sensory neuron, integrating center, motor neuron, effector

Which is the best sequence regarding a nerve impulse over a reflex arc?
• receptor, sensory neuron, integrating center, motor neuron, effector
• effector, sensory neuron, integrating center, motor neuron, receptor
• receptor, motor neuron, integrating center, sensory neuron, effector
• receptor, integrating center, sensory neuron, motor neuron, effector

• nucleus

In the central nervous system, a collection of neuron cell bodies with a common function, and with a discrete anatomical boundary, is called a _____.
• ganglion
• nucleus
• nerve
• center

• ganglia

Which of the following describes a collection of neuron cell bodies in the peripheral nervous system?
• ganglia
• centers
• columns
• tracts

chemical and electrical

what are the 2 major types of synapses?

one direction

what directions are impulses conveyed in chemical synapses?

any direction

what directions are impulses conveyed in electrical synapses?

ganglia, nerves

Neurons in the PNS
– Consist of ______
– Axons are bundled together in _______

center, nucleus, tracts and columns

Neurons in the CNS
– Collection of cell bodies called a ______
– If this center has a distinct boundary, it is called a _______
– White matter consists of axons in bundles called ___________

electrical synapse

▪ The presynaptic membrane of one neuron is tightly bound to the postsynaptic membrane of another neuron
▪ This binding permits the passage of ions from
one neuron to the next