Chapter 1: The Nervous System Flashcards
_______________ is the master controlling and communicating system of the body.
The nervous system
The Nervous System has three overlapping functions:
Sensory Input
Integration
Motor Output
The nervous system processes and interprets the sensory input and makes decisions about what should be done at each moment. This process is called ___________ .
Integration
The nervous system uses millions of sensory receptors to monitor changes occurring both inside and outside the body. These changes are called ________ and the gathered information is called ___________.
Stimuli
Sensory input
The nervous system causes a response by activating effector organs (muscles and glands). This response is called:
Motor output.
The Nervous System consists of two principal divisions.
The Central Nervous System (CNS)
The Peripheral Nervous System (PNS)
Consists of the brain and spinal cord which occupies the dorsal body cavity. Known as the integrating and command center of the Nervous System.
The Central Nervous System (CNS)
The part of the Nervous System outside the CNS and consists mainly of the nerves that extend from the brain and spinal cord.
The Peripheral Nervous System (PNS)
What is the function of the Central Nervous System (CNS)?
It interprets incoming sensory information and dictates responses based on past experience, reflexes and current conditions.
___________ carry impulses to and from the spinal cord and cranial nerves carry impulses to and from the brain. These peripheral nerve serve as communication lines that link all parts to the CNS.
Spinal nerves
The Peripheral Nervous System has two subdivisions:
The Sensory (afferent) division
The Motor (efferent) division
Keeps the CNS constantly informed of events going on inside the body. It consists of nerve fibres that transmit impulses to the CNS from sensory receptors, located throughout the body.
The Sensory (afferent) division
Two parts of the sensory (afferent) division:
Somatic Afferents
Visceral Afferents
Sensory fibres that convey impulses from the skin, skeletal muscles and joints.
Somatic Afferents
Sensory fibres that convey impulses from the visceral organs.
Visceral Afferents
Consists of nerve fibres that transmit impulses from the CNS to effector organs. These impulses activate muscles to contract and glands to secrete (these fibres bring about a motor response).
The Motor (efferent) division
Two parts of the Motor (efferent) division :
Somatic Nervous System
Autonomic Nervous System
Made up of somatic motor nerve fibres that conduct impulses from the CNS to skeletal muscles.
Somatic Nervous System
Made up of visceral motor nerve fibres that conduct impulses from the CNS to smooth muscles, cardiac muscles and glandular epithelial tissue.
Autonomic Nervous System
The Autonomic Nervous System itself has two divisions called:
Sympathetic Nervous System
Parasympathetic Nervous System
True or False:
Parasympathetic Nervous System is also known as “ fight and flight” system.
False:
Sympathetic Nervous System (fight and flight) Parasympathetic Nervous System (rest and digest)
There are no intervening synapses; nerve conduction is from the spinal cord or brainstem, directly to somatic effectors.
Somatic Nervous System
Its activity is evident when we are excited or find ourselves in an emergency or threatening situations.
Sympathetic Division (Thoracolumbar)
Chiefly concerned with keeping our body energy as low as possible, even as it directs vital activities such as digestion and elimination. It is most active in non-stressful situations.
Parasympathetic Division (Craniosacral division)
Cells of the Nervous System:
Neurons Glia cells (neuroglia)
________ are nerve cells. They are the structural unit of the nervous system.
Neurons
Function of neurons:
They conduct messages in the form of impulses from one part of the body to another.
What are the characteristics of neurons?
Extreme longevity
They can not divide (usually)
Exceptionally high metabolic rate
Characteristics of neurons. True or False
a) Extreme longevity - Nerve cells can live over a hundred years (or, as long as the person lives).
b) They can not divide (usually) - They can not be replaced if destroyed.
c) Exceptionally high metabolic rate - They constantly need oxygen and glucose; without it, they will die in a matter of 3 to 5 minutes.
True
Each neuron consists of three parts:
Dendrites
Cell body
Axon
Also called the soma. It contains a nucleus and most other organelles,except for centrioles.
Cell body
They are receptor, input regions that conduct impulses towards the cell body. All the organelles present in the cell body, are also present in the dendrites.
Dendrites
Conducts impulses away from the cell body. It contains the same organelles that are found in the cell body (with exception of the nucleus).
Axon
True or false:
Each neuron has one axon.Although each neuron has only one axon, the axon may branch to form axon collaterals . These axon collaterals extend from the axon, at right angles. The distal end of the axon branches into axonal terminals, synaptic knobs.
True
The axon arises from a cone shaped region of the cell body called _____________.
The axon hillock
______________ - Supporting cells that do not specialize in transmitting impulses. Instead, they help protect and hold the functioning neurons together. Outnumber neurons in the CNS 9 to 1 and make up about half the mass of the brain.
Glia cells (neuroglia)
Types of Glia (supporting) cells in the CNS:
Astrocytes
Microglia
Oligodendrocyte
Ependymal
Star-shaped and most abundant glia cells. They anchor small blood vessels (capillaries) to neurons and help form the blood-brain barrier.
Astrocytes
______________ is a selective barrier that separates the blood tissue and the nervous tissue, against harmful chemicals that might be in the blood.
The blood - brain barrier
What are the functions of blood - brain barrier ?
* Protects the brain from the possible leakage of harmful chemicals, from the blood into the brain.
* Keeps some helpful drugs, such as antibiotics, from gaining access to the brain, in order to deal with such harmful diseases as bacterial meningitis.
They are a type of macrophage and are usually stationary and monitor the health of nearby neurons. Extremely important because cells of the immune system are denied access to the CNS.
Microglia
Response of microglia when neurons are injured.
When microglia sense that neurons are injured, or in trouble, they enlarge and move about and act as microbe-eating scavengers.
____________ - Help hold nerve fibres together and form myelin sheaths, on axons in the CNS.
Oligodendrocyte
_____________ - line the central cavities of the brain and spinal cord. They form a permeable barrier between the cerebrospinal fluid that fills those cavities and the tissue fluid bathing the cells of the CNS. Their cilia help to circulate the CSF.
Ependymal
Supporting cells (Glia cells) of the PNS:
Schwann cells
Satellite cells
__________ - These cells wrap themselves around axons of some nerve fibres found in the PNS.
Schwann cells
The outer cell membrane of the Schwann cell is called the ________ and can play an important role in the regeneration of cut and injured axons.
Neurilemma
Schwann cells along the axon do not touch and leave gaps called ______________.
Nodes of Ranvier
___________ - Very similar to Schwann cells except for location. These cells surround neuron cell bodies within ganglia and play a role in controlling the chemical environment surrounding the neuron.
Satellite cells
Classification of Neurons:
Structural Classification
Functional classification
Three major types of structural classification of neurons:
a. Multipolar
b. Bipolar
c. Unipolar
Neurons can be grouped structurally according to the number of processes, extending from their cell body.
Structural Classification
Group neurons according to the direction in which the nerve impulse travels, in relation to the CNS
Functional classification
Type of structural classification of neurons that:
a) Have three or more processes (all dendrites except for a single axon)
b) Most common type in humans
c) Major type in CNS
d) Neurons have numerous branching dendrites and one axon.
e) Some neurons in this class do not have an axon, only dendrites.
Multipolar
Type of structural classification of neurons that:
a) Have two processes (one is a dendrite, the other is an axon)
b) Rare in adult body
c) Found only in special sense organs like the retina of the eye
Bipolar
Type of structural classification of neurons that:
a. Also called ___________ because they originate as bipolar and change during embryonic development.
b. Here a single process emerges from the cell body. The process divides into proximal and distal fibres.
c. The more distal process is called ________________.
d. The process entering the CNS is called _____________.
e. The cell bodies are found in the ganglia in the PNS
Unipolar pseudo-unipolar
peripheral process
central process
Types of functional classification of neurons:
Sensory neurons
Motor neurons
nterneurons (association neurons)
Which statement is false regarding Sensory neurons?
a. They transmit impulses from sensory receptors in the skin and internal organs towards the CNS.
b. Most sensory neurons are multipolar and their cell bodies are located in dorsal root ganglia inside the CNS.
c. Functionally, only the most distal parts of these unipolar neurons act as impulse receptor sites and the peripheral process formed by the joining of the dendritic branches, are often very long.
B.
Correct: Most sensory neurons are unipolar and their cell bodies are located in dorsal root ganglia outside the CNS
Type of functional classification of neurons: These neurons lie between motor and sensory neurons.Typically multipolar and are only found in the CNS. Make up over 99% of the neurons in the body.
Interneurons (association neurons)
__________ carry impulses away from the CNS to effector organs, they are multipolar. Most cell bodies are located in the CNS (except for the ANS). They form junctions with their effector organs called the _______________.
Motor neurons
neuromuscular junctions
Type of functional classification of neurons: These neurons lie between motor and sensory neurons.Typically multipolar and are only found in the CNS. Make up over 99% of the neurons in the body.
Interneurons (association neurons)
__________ carry impulses away from the CNS to effector organs, they are multipolar. Most cell bodies are located in the CNS (except for the ANS). They form junctions with their effector organs called the _______________.
Motor neurons
neuromuscular junctions
