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From Flashcardlet > Nervous Tissue > Flashcards

Nervous Tissue Flashcards

0
Q

Efferent/motor neurons

A

Neurons that carry responses from the brain and spinal cord to the periphery

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1
Q

What is the nervous system?

A
  • involved primarily with communication, control, and coordination of bodily functions
  • works with endocrine system to maintain homeostasis
  • actions are rapid, but short lived
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2
Q

Functions of the NS

A
  1. Receive stimuli+ detect changes in the body
    - sensory function of neurons –> afferent neurons
  2. Integration of incoming with outgoing neural signals
    - interneurons –> involved with integration
  3. Respond to stimuli by initiating actions
    - motor function of neurons
    - efferent/motor neurons
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3
Q

Effectors

A

The cells or organs that are stimulated by the motor neurons and will directly produce the response

Ex. Muscle fibres (all 5 kinds) and gland cells

  • therefore muscles + glands are the effectors that are influenced directly by the NS
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4
Q

Divisions of the nervous system

A

Central nervous system
- brain and spinal cord

Peripheral nervous system
- cranial nerves, spinal nerves, nerve ganglia, sensory receptors, enteric plexuses (in small intestine)

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5
Q

Divisions of the peripheral NS

A

Divisions are functional + include both afferent & efferent functions within them

  1. Somatic nervous system
  2. Autonomic nervous system
  3. Enteric nervous system
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6
Q

Somatic NS

A

Composed of:

A) sensory neurons
- afferent function
- from somatic sensory receptors
- carry sensory info about which you’re consciously aware
B) motor neurons
- produce voluntary contractions of skeletal muscles only
- efferent function

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7
Q

Autonomic NS

A

Composed of:

A) sensory neurons
- from autonomic sensory receptors
- sensations about which you’re not consciously aware
B) motor neurons
- stimuli to cardiac & smooth muscle & glands
–> sympathetic division
- involuntary effectors preparing for “fight or flight”
–> parasympathetic division
- involuntary effectors preparing to “rest & repair/relax”
- normal, everyday activity

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8
Q

Sympathetic & parasympathetic divisions

A
  • both divisions generally innervate the same organs/tissues but have opposite effects
  • allows the nervous system to ‘fine-tune’ its coordination effects on the body’s involuntary functions
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9
Q

Enteric Nervous System

A
  • structurally distinct division of the PNS
  • comprised of 100 million neuron found in the enteric plexuses (GI tract)
  • sometimes called “brain of the gut”
  • contains involuntary sensory (afferent) and involuntary motor (efferent) fibres
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10
Q

Afferent Neurons

A

Neurons carrying sensory info to the brain or spinal cord from the peripheral or from lower to higher levels in the spinal cord or brain

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11
Q

Sensory (afferent) fibres

A

Bring info from the GI system to the CNS regarding the chemical conditions present in the gut and the degree of stretch in the gut walls

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12
Q

Motor (efferent) fibres

A

Send responses from the CNS to the involuntary effectors to influence the contraction of smooth muscle in the walls of the GI tract, and to control the secretory activity of the GI glands
(Pancreas, stomach, SI)

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13
Q

Nervous tissue

A
  • highly cellular
  • <20% of CNS is extracellular space
  • 2 main cell types
    1) neurons –> excitable & able to transmit electrical signals in the form of action potentials
    2) neuralgia –> smaller cells which. Nourish, wrap & support the neurons
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14
Q

Neuroglia- in general

A
  • numerous within nervous tissue
  • account for approx. 1/2 of the volume of CNS
  • maintain ability to divide & multiply throughout your life therefore more prone to cancer than neurons
  • variation in type of neuroglia cells
  • not excitable
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15
Q

CNS neuroglia cells (types)

A
  1. Astrocytes
  2. Microglia
  3. Ependymal cells
  4. Oligodendrocytes
16
Q

Astrocytes

A
  • named foe their “star-like” shape
  • only in CNS
  • Most abundant & versatile
  • have multiple radiating process (branches) which cling to neurons & form sheaths around BV’s to link the 2 together
  • blood brain barrier (BBB)
17
Q

The blood Brain barrier (BBB)

A
  • Formed by sheaths created by astrocytes’ processes combined with tight junctions between endothelial cells of capillary walls
  • controls capillary’s permibility
  • maintains physical & biochemical isolation of neural tissue from general circulation
  • water, glucose & O2 CAN cross BBB
  • many drugs & ions CAN’T cross BBB
18
Q

Microglia

A
  • small cells with long processes
  • capable of phagocytosis
  • detect neural injury/death & respond by moving towards neurons to phagocytose them
    - waste removal
  • important protectors of CNS
19
Q

Ependymal cells

A
  • various shapes
  • often ciliated
  • type of epithelial cell
  • cells form sheets to line the fluid-fluid cavities in CNS
  • cilia help to circulate cerebrospinal fluid (CSF) which cushions brain & spinal cord
    • also transport nutrients, wastes, gasses, etc
20
Q

Oligodrocytes

A
  • smaller cells with fever processes but similar shape to astrocytes
  • produce myelin sheath around neurons in CNS only (myelinated)
  • Unmyelinated portions of neurons: Nodes of Ranvier

White matter = myelinated
Grey matter = Unmyelinated

21
Q

PNS neuroglia cells (types)

A
  1. Schwann cells

2. Satellite cells

22
Q

Schwann cells

A
  • Found only in PNS
  • support nerve fibres and form the myelin sheath around them
  • gaps between cells form the Nodes of Ranvier
    - these. Areas are Unmyelinated
  • vital to the process of peripheral nerve fibre regeneration
  • Has neurolemma
23
Q

Neurolemma

A
  • comprised of nucleus & cytoplasm of Schwann cell, squeezed to perimeter of myelin sheath
  • only in PNS
  • required for neuron regeneration to occur
  • myelination of PNS neurons begins during fetal development
24
Q

Satellite Cells

A

Surround the nerve cell bodies and gold the together organized into bundles that are known as ganglia

(Ganglion = singular)

25
Q

Neurons (parts)

A

The neuron is the structural and functional unit of the nervous system

Contains 3 parts

  • body
  • dendrite
  • axon
26
Q

Neuron - Body

A
  • contains cytoplasm, organelles
  • metabolic cent of the neuron cell
  • contains Nissl bodies (RER) therefore great del of protein synthesis preformed.
27
Q

Neuron - dendrite

A
  • usually short & tapering with branches
  • function as afferent route to bring impulses towards the neuron’s cell body
  • distal ends may be structurally specialized to form sensory receptors
  • never myelinated
28
Q

Neuron - Axon

A

1 axon/neuron

  • may be branched
  • joins cell body at the axon hillock
  • contains no RER (so no protein synthesis)
  • functions as the efferent route from the neuron’s cell body to the effector

Myelinated axons = faster conduction
Larger diameter axons = faster conduction

29
Q

Special characteristics of neurons

A
  • irritability
  • conductivity
  • longevity
  • amitotic
  • high metabolic rate

Produce CO2 as waste

30
Q

Structural diversity in neurons

A
  • cell bodies range in size
  • dendrites range in complexity
  • branching pattern of dendrites varies
  • presence/absence and length of axon
  • # of processes extending from neuron cell body varies
31
Q

Functional classification of neurons are based on the direction of impulse conduction

A
  1. Afferent/sensory neurons
    • conduct impulses towards the neurons cell body & ultimately towards CNS (cell body outside CNS)
  2. Efferent/motor neurons
    • conduct impulses away from cell body & ultimately away from CNS and to effector cells (muscles + glands)
  3. Interneurons/association neurons
    • conduct impulses from afferent, toward efferent neurons
    • entire neuron structure lies within CNS
32
Q

Synapse

A

Place where the nerve impulse, or action potential, is passed form one neuron to another cell

Meaning it is being passed either to another neuron or to an effector cell (muscle or gland)

33
Q

The components of a synapse include:

A
  1. Synaptic bulb ends of the axon of the incoming neuron
  2. Dendrites on cell body/plasma membrane, with associated receptors, of between 2 cells
    Neuron - neuron OR neuron - effector

From Flashcardlet (9 decks)

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