Lecture 11: Nervous Tissue Flashcards Preview

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Flashcards in Lecture 11: Nervous Tissue Deck (12):
1

What are the functions of the nervous system

1. Sensory input
-information gathered by sensory receptors about interval and external changes
2. Integration: interpretation of sensory input
3. Motor output: activation of effector organs (muscles and glands) produces a response
-or activation of another neuron

2

What are the two divisions of the nervous system, what are their functions?

1. Central nervous system: brain and spinal cord, it's the integration and command centre
2. Peripheral nervous system (PNS): paired spinal and cranial nerves carry messages to and from the CNS

3

What are the two functional divisions of the PNS

1. Sensory (afferent) division
-somatic afferent fibres- convey impulses from skin, skeletal muscles, and joints
-visceral afferent fibres- convey impulses from visceral organs
2. Motor (efferent) division:
-transmits impulses from the CNS to effector organs

4

What are the motor divisions of the PNS?

1. Somatic (voluntary) nervous system
-conscious control of skeletal muscles
2. Autonomic (involuntary) nervous system (ANS)
-visceral motor nerve fibres
-regulates smooth muscle, cardiac muscle, and glands
-two functional subdivisions
Sympathetic and parasympathetic

5

What are the two types of nervous tissue

1. Neurons- excitable cells that transmit electrical signals
-long lived 100 yrs or more
-high metabolic rate- needs lots of o2 and glucose
2. Neuroglia (glial cells)- supporting cells
A) astrocytes CNS: most abundant and highly branched glial cells, cling to neurons, synaptic endings, and capillaries
-support and brace neurons
-control the chemical permeability
B) microglia CNS (defensive cells)
-small thorny processes which migrate towards injured neurons
-phagocytize microorganisms and neural debris
C) ependymal cells CNS
-line the central cavities of the brain and spinal column
-job is to separate the CNS interstitial fluid from the cerebrospinal fluid in the cavities
D) oligodendrocytes CNS
-have processes that form myelin sheath around CNS nerve fibres
E) schwann cells PNS

6

Define neuron, describe its important structural components, and relate each to a functional role.

Cell body: spherical nucleus with nucleolus
-well developed Golgi apparatus
-rough endoplasmic reticulum called Nissl bodies
-network of neurofibrils (neurofilaments)
-clusters of cell bodies are called nuclei in the CNS, ganglia in the PNS
Processes:
Dendrites:
-receptive input region of neuron, convey electrical signals toward the cell body as graded potentials
Axons:
-knoblike axon terminals (synaptic knobs or boutons) which is the secretory region of a neuron, which releases neurotransmitters to excite or inhibit other cells

7

Explain the importance of myelin sheath and describe how it is formed in the central and peripheral nervous system

Myelin sheath is segmented protein-lipid sheath around most long or large diameter axons. It functions to:
-protect and electrically insulate the axon
-increase speed of nerve impulse transmission

Myelin sheath in the PNS
Schwann cells: wraps many times around the axon
Neurilemma: peripheral bulge of Schwann cell cytoplasm
Nodes of ranvier: myelin sheath gaps between adjacent Schwann cells

Myelin sheaths in the CNS:
-formed by processes of oligodendrocytes, not the whole cells
-nodes of ranvier are present
-no neurilemma
-thinnest fibres are unmyelinated

8

What is the difference between grey matter and white matter

White matter: dense collections of myelinated fibres
Gray matter: mostly neurons cell bodies and unmyelinated fibres

9

What are the three different structures of neurons

1. Multipolar: 1 axon and several dendrites
-most abundant
-motor neurons and interneurons
2. Bipolar: 1 axon and 1 dendrite
-rare eg retinal neurons
3. Unipolar: single, short process that has two branches:
-peripheral process which is a more distal branch coming from a sensory receptor
-then a central process-which is a branch entering the CNS
-found mainly in the PNS

10

What are the three types of neurons?

1. Sensory (afferent): transmits impulses from sensory receptors towards the CNS
2. Motor (efferent): carry impulses from the CNS to the effectors
3. Interneurons (association neurons): shuttle signals through CNS pathways; most are entirely within the CNS

11

What are the three nerve fibre classifications:

Group A fibres: large diameter, myelinated somatic sensory and motor fibre
Group B: intermediate diameter, lightly myelinated ANS fibres
Group C: smallest diameter, unmyelinated ANS fibres

12

What is a synapse, and what happens here?

A junction that mediates the transfer from one neuron:
-to another neuron or
-to an effector cell: muscle or gland