Nerves Part 1 and 2 Flashcards
Central Nervous System (CNS)
composed of the brain and the spinal cord
Peripheral Nervous System (PNS)
composed of the nerves that connect the brain or spinal cord with the body muscles, glands, and sense organs
Somatic Nervous System (Voluntary control of movements)
- afferent neurons bring signals from peripheral receptors to the CNS
- Efferent Neurons bring signals from the CNS to the skeletal muscle fibres
Autonomic Nervous System - Involuntary (Smooth and Cardiac)
- Contains sensory neurons from visceral organs and motor neurons that convey impulses from the CNS to smooth muscle tissue, cardiac muscle tissue, and glands
- This system works with endocrine system to maintain homeostasis
Enteric nervous system (Part of ANS)
Neurons that regulate gastrointestinal system
Functions of the Nervous System (Sensory Function)
Sensory receptors detect internal and external stimuli
Information is carried to brain and spinal cord through cranial and spinal nerves
Functions of the Nervous System (Integrative Function)
Integrates sensory information by analyzing and storing some of it
and by making decisions for appropriate responses (a.k.a. integration)
Functions of the Nervous System (Motor Function)
Elicitation of motor response in response to integrated sensory
information
Activates effectors (muscles and/or glands)
Neurons
Possess electrical excitability
3 parts
1. Cell Body
2. Dendrites
3. Axon
Neurons (Cell Body)
Contains nucleus, cytoplasm & typical organelles
Neurons (Dendrites)
The receiving or input parts of the neuron
Usually short with many branches
Neurons (Axons)
- Conducts nerve impulses
- Nerve impulses arise at the
axon hillock - Some have axon collaterals
- Terminate at axon terminals
- Axon terminals form
Synapses with other neurons
or effector cells
3 Structural Classification
- Multipolar
- Bipolar
- Unipolar
Functional Classification
- Sensory (afferent) neurons
- Motor (efferent) neurons
- Interneurons (associtation neurons)
Sensory (afferent neurons)
- unipolar/bipolar
- sensory receptors (input) at distal end
- action potential conveyed through cranial or spinal nerves
Motor (efferent neurons)
- multipolar
- convey action potential to effectors (muscles and glands)
Interneurons (Association neurons)
- Multipolar
- Within CNS between sensory and motor neurons
- Integrate/process incoming sensory information
- activate appropriate motor neurons to elicit a response
Neuroglia (Neuron Helpers)
- smaller than neurons and at least 5 times as many
- they do not generate or conduct nerve impulses
Neuroglia in the CNS
- astrocytes
- Oligodendrocytes
- Microglia
- Ependymal cells
Neuroglia in the PNS
- Schwann Cells
- Satellite cells
Astrocytes (CNS)
- protect Neurons from harmful substances
- Maintain proper chemical environment for nerve impulse generation
- play a role in learning and memory
- Help form the blood-brain barrier
Oligodendrocytes (CNS)
- Produce/maintain myelin sheath around several adjacent neurons
Microglia (CNS)
- Protect CNS from disease: engulf invading microbes
- Clear away debris of dead cells in damaged nerve tissue
Ependymal Cells (CNS)
- line ventricles of the brain and central canal of the spinal cord
- form a cerebrospinal fluid and assist in circulation
Schwann Cells (PNS)
- produce and maintain myelin sheath around a single axon of a neuron
- participate in regeneration of PNS axons
Satellite cells (PNS)
- Support neurons in PNS ganglia
- Regulate exchange of materials between neurons and interstitial fluid
Myelin Sheath
- many-layered covering composed of lipid and protein
- protects axon, like insulation of an electrical wire
- Increase the speed of nerve impulse conduction
- up to 100 layers
Nodes of Ranvier
- gaps in the myelin sheath
Resting Membrane Potential
- 70 mv
Spinal Cord
- Runs from the foramen magnum to 2nd
lumbar vertebrae - Suspended within the vertebral canal
- Extends from the medulla oblongata and (part of the brain stem) to the upper border of L2 (the conus medullaris)
Spinal Meninges
- Three meninges (meninx = singular),
- Cover the spinal cord.
- Continuous with the cranial meninges (protect the brain)
Cauda Equina
collection of spinal nerves that travel down the vertebral canal
Cervical Enlargement
neurons innervate upper limbs