Download Nervous System Overview: Functions, Divisions, and Components and more Exams Advanced Education in PDF only on Docsity!
APK2100C Chapter 1 2 Test With
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The Nervous System [Overview] - ANSWER - Master controlling and communication system of the body
- Responsible for actions like muscle contractions or reflexes Describe the signals produced by the nervous system. - ANSWER Signals are rapid/specific and cause IMMEDIATE responses by the body. True or False: Rapid signals from the nervous system cause immediate responses by the body. - ANSWER True Endocrine System [Basic Function] - ANSWER - The body's 'slow' chemical communication system
- Communicates by chemical messages (HORMONES) that are secreted into blood
- Involves glands for secretion Nervous System [Basic Function] - ANSWER - The body's 'rapid' communication system
- Employs electrical AND chemical means to send messages from cell to cell
- Involves nerves and neurons for transmission 3 Overlapping Functions of the Nervous System - ANSWER (1) Sensory Input (2) Integration
(3) Motor Output Sensory Input [NS Function] - ANSWER Sensory receptors monitor changes inside and outside of body Integration [NS Function] - ANSWER CNS receives and interprets sensory input and makes a decision for action Motor Output [NS Function] - ANSWER Motor neurons elicit responses by activating effector organs 2 Main Divisions of the Nervous System - ANSWER (1) Central Nervous System (CNS) (2) Peripheral Nervous System (PNS) [Structure] Central Nervous System - ANSWER Brain and spinal cord [Function] Central Nervous System - ANSWER Integrative and control centers [Structure] Peripheral Nervous System - ANSWER Cranial nerves and spinal nerves *Everything else EXCEPT for the brain and spinal cord [Function] Peripheral Nervous System - ANSWER Communication lines between the CNS and the rest of the body 2 Divisions of the PNS - ANSWER (1) Sensory (afferent) (2) Motor (efferent) [Structure] Sensory (AFFERENT) Division of the PNS - ANSWER Somatic (skin) and visceral (hollow organ lining) sensory nerve fibers [Function] Sensory (AFFERENT) Division of the PNS - ANSWER Conducts
What is the main difference between the somatic nervous system and the ANS in terms of motor movement control? - ANSWER The somatic nervous system is VOLUNTARY, while the ANS is INVOLUNTARY 2 Divisions of the ANS - ANSWER (1) Sympathetic (2) Parasympathetic [Function] Sympathetic Division - ANSWER - Mobilizes body systems during activity
- "Fight-or-Flight" response [Function] Parasympathetic Division - ANSWER - Conserves energy and promotes house-keeping functions during rest
- "Rest-and-Digest" response Neurons vs. Neuroglia in terms of excitability - ANSWER Neurons: Excitable Neuroglia: Non-excitable 4 Special Characteristics of Neurons - ANSWER (1) Conductivity (2) Extreme Longevity (3) Inability to Divide (4) High Metabolic Rate Conductivity of Neurons - ANSWER - Able to send electrical signals from one part of the body to another
- Referred to as 'action potentials' or 'nerve impulses' Extreme Longevity of Neurons - ANSWER Can live and function for a lifetime
Inability to Divide for Neurons - ANSWER - Cannot be replaced if destroyed (very few exceptions)
- Example: Paralysis High Metabolic Rate of Neurons - ANSWER Requires constant supply of oxygen and nutrients True or False: Axons can be really short or really long. - ANSWER True Soma/Neurosoma - ANSWER - Cell body of a neuron
- Contains the nucleus, nucleolus, mitochondria, rough ER, etc... Dendrites - ANSWER - Processes/extensions from the cell body that are RECEPTORS (input area)
- Receives signals and transmits them to the cell body Axon - ANSWER - Impulse-generating and conducting region of a neuron (output area)
- Signals move away from the cell body Axon Hillock - ANSWER - Extremely long process of a neuron
- Area of the cell body that starts to taper off (conic-shape) to turn into the axon Schwann Cell - ANSWER - Neuroglia wrapping long portions of the axon
- Segments of insulation
- Can form myelin sheaths
- Helps conduct electrical signals at high speeds
- Most common type of neuron
Bipolar Neuron - ANSWER - 2 processes extend from the cell body
- 1 is a fused dendrite while the other is an axon
- Common for sensory neurons for facial nerves
Unipolar Neuron - ANSWER - 1 process extends from the cell body
- Splits to form central and peripheral processes -> Together comprise an axon
- Central Process + Peripheral Process = Axon
3 Functional Classifications of Neurons - ANSWER (1) Afferent (2) Efferent (3) Interneurons
- Based on direction of nerve impulses relative to the CNS
Afferent Neuron - ANSWER - Sensory-based
- Impulses move TOWARDS the CNS
Efferent Neuron - ANSWER - Motor-based
- Impulses move AWAY from the CNS
Interneurons - ANSWER - Association-based
- Impulses move WITHIN the CNS
- If you find this within the brain or spinal cord, then it's this neuron
Synapses - ANSWER - "Sites of Communication"
- Communication between neuron-to-neuron OR neuron-to-other body cell
- Dendrites receive signals of other axon terminals
2 Types of Synaptic Neurons - ANSWER (1) Presynaptic (2) Postsynaptic
Presynaptic Neuron - ANSWER Neuron that SENDS the signal down the synapse to the next neuron
Postsynaptic Neuron - ANSWER Neuron on the RECEIVING end of the synapse
Neuroglia - ANSWER - Non-excitable -> Will NOT respond to electrical signals unlike neurons
- Contains cell processes like neurons
- Smaller and more numerous
- Able to divide throughout life
- Covers all NON-SYNAPTIC surfaces of neurons
How many types of CNS neuroglia are there? - ANSWER 4
How many types of PNS neuroglia are there? - ANSWER 2
4 Types of CNS Neuroglia - ANSWER (1) Astrocytes (2) Microglial Cells (3) Ependymal Cells (4) Oligodendrocytes
[Structure] Astrocytes - ANSWER - Type of CNS neuroglia
- Star-shaped processes that extend from the cell
- Most abundant of the 4 types
[Function] Astrocytes - ANSWER - Increases neurotransmitter uptake
- Signals increased blood flow to active brain regions
- Controls ionic environment around neurons
[Structure] Microglial Cells - ANSWER Smallest and least abundant of 4 types
[Function] Microglial Cells - ANSWER - Act as macrophages of the CNS
- Scavenges/eats-up microorganisms or pathogens
- The defensive cells in the CNS
[Structure] Ependymal Cells - ANSWER - Simple, ciliated epithelium
- Lines the cerebrospinal fluid-filled cavities
[Function] Ependymal Cells - ANSWER - Circulates CSF due to its motility from the cilia
- Forms a permeable lining of ventricles (fluid-filled cavities of CSF within the brain)
[Structure] Oligodendrocytes - ANSWER - Octopus-like processes
Presence of Myelin Sheaths in Schwann Cells - ANSWER - Involves the wrapping of the ENTIRE CELL around axon segments
- Some tightly coil around an axon, forming concentric layers -> Helps with insulation
- Some just lightly wrap around bundles of axons, which results in loose wrappings -> Does NOT help with insulation
Myelin Sheaths - ANSWER - Concentric layers of plasma membrane from Schwann cells or oligodendrocytes
- Tightly wrap segments of axons with 'myelin'
How is the position of Schwann cell organelles affected from the tight wrapping of myelin around the axon? - ANSWER The organelles are pushed peripherally
Basic Formation of a Myelinated Axon in the PNS - ANSWER (1) Schwann cell envelopes an axon (2) Rotation of the Schwann cell around the axon results in loose wrappings of its plasma membrane in successive layers (3) Schwann cell cytoplasm is forced between the membranes -> Forms the tight concentric wrappings (myelin sheath)
Basic Formation of a Nonmyelinated Axon in the PNS - ANSWER (1) Schwann cell surrounds MULTIPLE axons (2) Each axon is encircled by the Schwann cell membrane
Multiple Sclerosis - ANSWER - Degenerative disorder of myelin sheaths
- Neuroglia degenerates where myelin is replaced by hardened scar tissue
- Nerve conduction is disrupted
- Can result in double vision, tremors, numbness, and speech defects
Tay-Sachs Disease - ANSWER - Degenerative disorder of myelin sheaths
- Hereditary disease that is mainly found in Jewish infants
- Abnormal accumulation of glycolipids within the myelin sheath
- Disrupts communication of nerve signals
- Can cause blindness, loss of coordination, and dementia (most are fatal before age 4)
Nerve Fiber Conduction Speed - ANSWER Speed of a nerve signal travelling along the surface a nerve fiber
2 Factors Determining Nerve Fiber Conduction Speed - ANSWER (1) Fiber diameter -> Larger = Faster
- Color given due to myelin
Nerves of the PNS - ANSWER - Cable-like ORGANS with parallel arranged axons
- Contain connective tissue sheaths
Epineurium - ANSWER CT sheath lining the outside of the entire nerve
Perineurium - ANSWER CT sheath lining around a fascicle
Fascicles of the PNS - ANSWER Bundles of nerve fibers
Endoneurium - ANSWER CT sheath lining each individual nerve fiber
Reflex - ANSWER Rapid, automatic, motor response to stimuli
Reflex Arc - ANSWER Pathway for a simple chain of neurons to cause a reflex
4 Important Reflex Properties - ANSWER (1) Stimulation Required (2) Quick
(3) Involuntary (4) Stereotyped
[Reflex] Stimulation Required - ANSWER Reflexes are NOT spontaneous actions, but they respond to sensory inputs
[Reflex] Quick - ANSWER Reflexes involve FEW (if any) interneurons, which minimizes synaptic delay
[Reflex] Involuntary - ANSWER Reflexes occur without intent and are difficult to suppress -> Automatic responses
[Reflex] Stereotyped - ANSWER Reflexes occur essentially the exact same way every time
Pathways of the Reflex Arc - ANSWER (1) Somatic Receptors -> Located on the skin, muscles, and tendons -> (Act as receptors for signals)
(2) Afferent Sensory Nerve Fibers -> Carry the signal from the receptors to the posterior horn of the spinal cord or brainstem -> (Receptor to CNS)
Flexor (Withdrawal) Reflex - ANSWER - Polysynaptic withdrawal reflex
- Contraction of flexor muscles resulting in the withdrawal of the limb from injurious stimuli
- Contains an ipsilateral reflex arc -> Communication of sensory and motor neurons are on the SAME side
How many neurons and synapses are involved in flexor reflexes? - ANSWER 3 Neurons -> Afferent/Interneuron/Efferent neurons 2 Synapses -> Reason this reflex is called 'polysynaptic'
Do all reflexes have to cause a response to the SAME side of the body where the stimulus occurred? - ANSWER Not always, some can occur on opposite sides of the body (contralateral) -> Referred to as 'crossed extension reflex'
Example: Your left foot steps on a piece of glass (ouch) and reflexes force you to lift up that left foot. Simultaneously, your right foot muscles contract to help keep your body stable while you're standing on one foot. You wouldn't want to fall on your butt, would you???
