Nervous Tissue Flashcards
1
Q
Functions
A
- controls and integrates all body activities (along with endocrine system)
- 3 basic functions:
- Sensory: sensing changes with receptors
- integration: interpreting and remembering those changes
- motor: reaction to those changes with effectors
- muscular contractions
- glandular secretions
2
Q
Divisions of Nervous System
A
- Central nervous system: brain and spinal cord
- Peripheral nervous system: cranial and spinal nerves that contain sensory and motor fibres. Connect CNS to muscles, glands, and all sensory receptors
3
Q
Subdivisions of the PNS
A
- somatic (voluntary NS
- sensory info from sensory receptors to CNS
- motor neurons to skeletal muscles
- autonomic (involuntary) nervous system
- sensory neurons from visceral organs to CNS
- motor neurons to smooth & cardiac muscle and glands
- divided into sympathetic & parasympathetic & enteric division (neurons in gut)
4
Q
Histology of Nervous Tissue
A
- consists of 2 main cell types
- neurons
- neuroglia
5
Q
Neuroglial Cells
A
- half the volume of CNS
- smaller cells than neurons
- 50x more numerous
- cells can divide
- rapid mitosis in tumour formation (gliomas)
- 4 cells types in CNS
- astrocytes, oligiodendrocytes, microglia, ependydymal
- 2 cell types in PNS
- schwann and satellite cells
6
Q
Astrocytes
A
- star shaped cells
- form blood-brain barrier by covering blood capillaries
- metabolize neurotransmitters
- regular K+ balance
- provide structural support
7
Q
Oligiodendrocytes
A
- each forms myelin sheath around more than one axon in CNS
- analogous to Schwann cells of PNS
8
Q
Microglia
A
- small cells found near blood vessels
- phagocytic role: clear away dead cells
- derived from cells that also gave rise to macrophages and monocytes
9
Q
Ependymal Cells
A
- form epithelial membrane lining cerebral cavities and central canal of the spinal cord
- produces cerebrospinal fluid (CSF)
10
Q
Satellite Cells
A
- flat cells surrounding neuronal cell bodies in peripheral ganglia
- support neurons in PNS ganglia
11
Q
Shwann Cells
A
- cells encircling PNS axons
- each cell produces part of the myelin sheath surrounding an axon on the PNS
12
Q
Neurons
A
- functional unit of nervous system
- have capacity to produce action potential (electrical excitability)
- cell body is a single nucleons with prominent nucleolus
- cell body contains nissle bodies (chromatophilic substance)
- rough ER and free ribosomes for protein synthesis
- neurofilaments give cell shape and support
- microtubules move material inside cell
- cell processes: dendrites and axons
13
Q
Dendrites
A
- conduct impulses toward the cell body (receptive zone)
- typically short, highly branched and unmyelinated
- surfaces specialized for contact with other neurons
- contains neurofibromas and Nissan bodies
14
Q
Axons
A
- conducts impulses away from cell body (conductive zone)
- long, thin cylindrical process of cell
- arises at axon hillock
- impulses arise from initial segment (trigger zone)
- side branches (collaterals) end in fine processes called axon terminals
- swollen tips called synaptic end bulbs contain vesicles filled with neurotransmitters
15
Q
Axon coverings in PNS
A
- axons surrounded by a lipid & protein covering produced by Schwann cells
- myelinated axons appear white (jelly-roll like wrapping made of lipoprotein myelin) acts as electrical insulator and speeds up conduction of nerve impulses
- regular spaces or gaps in myelin sheath called nodes of ranvier
- unmyelinated fibres: slow, small diameter fibres
- surround glial cell processes but no myelin sheath wrapping
- gray and white matter