BN Ch.19 The Nervous System Flashcards
1
Q
Name and describe parts of a neuron and how neurons transmit impulses.
A
- Cell body:
- Contains the nucleus, mitochondria, and other organelles.
- The cell body may be relatively far away from its axon or dendrites.
- An axon is
- An extension that carries impulses away from the neuron cell body.
- An axon may be as short as a few millimeters, or it may be longer than a meter.
- It may be myelinated (covered in a protective layer), or it may be bare.
- Dendrites are:
- Short, often highly branched extensions of the cell body.
- They receive impulses from axons of other neurons and transmit these impulses toward the cell body.
- Dendrites respond to chemical messages sent across the synapse (the synaptic cleft or myoneural junction), the tiny space separating neurons from each other.
2
Q
Give an example of a sensory, motor, and interneuron impulse.
A
Give an example of a sensory, motor, and interneuron impulse.
- Sensory (afferent) neurons:
- Receive messages from all parts of the body and transmit these messages (about hormone levels, blood pH, touch, sound, light, and pressure) to the central nervous system.
- Sensory neurons usually have long dendrites and a short axon.
- Motor (efferent) neurons:
- Receive messages from the central nervous system (CNS) and transmit them, as motor output, causing an action, to muscles and glands in all parts of the body.
- Signals carried by these neurons alter muscle activity or cause glands to secrete.
- Motor neurons usually have short dendrites and a long axon.
- Interneurons (connectory, association neurons, or integrators)
- Function as a link between the two other types of neurons.
- They are interconnecting neurons and are located only within the central nervous system.
3
Q
List primary functions of each of the brain’s four cerebral lobes.
A
- Frontal:
- Located at front of the skull, forehead
- Location of higher mental processes (intelligence, motivation, mood, aggression, and planning);
- Site for verbal communication and voluntary control of skeletal muscles
- Parietal
- Between frontal and occipital lobes
- Location of skin, taste, and muscle sensations; speech center
- Enables formation of words to express thoughts and emotions; interprets textures and shapes
- Temporal
- Located at sides of the skull
- Location of sense of smell and auditory interpretation
- Stores auditory and visual experiences; forms thoughts that precede speech
- Occipital
- Located at back of the skull
- Location of eye movements
- Integrates visual experiences
4
Q
Explain how an injury to the cerebellum might manifest itself in an individual.
A
- Balance problems
- Gait disorders along with
- Difficulties in coordination resulting in ataxia, (uncoordinated movements, imbalance, speech problems(dysarthria)
- Visual problems (nystagmus)
5
Q
Identify the role of the limbic system in maintaining a person’s level of awareness.
A
- The limbic system is located on both sides of the thalamus in a primitive area between the cerebrum and inner brain. (The term “limbic” means “pertaining to a margin or edge.”)
- The limbic system is largely responsible for maintaining awareness and emotions.
- It includes the hippocampus and reticular formation.
- The hippocampus functions in learning and long-term memory.
- The reticular formation is involved in allowing sensory input to enter the cerebral cortex and also governs wakefulness and sleep through a portion called the “reticular activating system” (RAS).
- The RAS is affected by environmental stimuli via the eyes (light) and ears (sound), which activate the RAS to assist a person in awakening and maintaining alertness.
- The RAS also screens incoming sensory input and channels it to specific areas of the brain.
- An area called the cingulated gyrus coordinates smells and sights with pleasant memories and helps to regulate aggression.
6
Q
State functions of the medulla, pons, and midbrain. Describe two nursing considerations appropriate for a client with brainstem dysfunction.
A
- The midbrain functions as a reflex center.
- The pons contains nerve tracts and carries messages between the cerebrum and medulla and is also responsible for respiration.
- The medulla contains centers for vital body functions, such as heart rate, vasomotor tone, and respirations.
7
Q
Identify the three meninges, and explain the functions of the spinal cord and cerebrospinal fluid.
A
- The Dura mater:
- The outer layer is a tough, fibrous covering that adheres to the skull bones. (The layers of the dura are the endosteal periosteum of the skull, continuous with the lining of the vertebral canal, and the meningeal layer, covering the brain.)
- The dura provides protection and support for the brain.
- The Arachnoid Membrane:
- The middle layer of protective membrane is a delicate web of tissue
- The Pia Mater:
- Lies closely over the brain and spinal cord.
- It is thin and vascular, containing many blood vessels that bring oxygen and nutrients to nervous tissue.
Spinal Cord Functions:
- The spinal cord has two main functions:
- To conduct impulses to the brain (afferent)
- From the brain (efferent) and to act as a reflex center.
Cerebrospinal Fluid (CSF)
- Acts as shock absorber for the brain and spinal cord
- Carries nutrients to the brain
- Carries wastes away from the brain
- Keeps the brain and spinal cord moist, thus preventing friction
- Can be tested to determine the presence of some disorders
- Can be used to transmit medications
8
Q
List the 12 cranial nerves and function of each. Describe the functions of spinal nerves.
A
- Olfactory
- Smell (Sensory)
- Optic
- Vision (Sensory)
- Oculomotor
- Eye movements (Motor)
- Trochlear (smallest cranial nerves)
- Voluntary eye movements (Motor)
- Trigeminal (largest cranial nerves)
- Sensations of head and face; movement of mandible (Both)
- Abducent (Abducens)
- Eye movements (Motor)
- Facial
- Taste;
- Facial expressions (Both)
- Vestibulocochlear (Acoustic)
- Hearing and balance
- Glossopharyngeal
- Controls swallowing
- Gives information on pressure and oxygen tension of blood
- Taste (Both)
- Vagus (“ wanderer”) (the only cranial nerve not restricted to head and neck)
- Somatic motor function
- Parasympathetic functions
- Speech
- Swallowing
- Gag reflex (Both)
- Accessory (Spinal accessory)
- Rotation of head;
- Raising of shoulder (Motor)
- Hypoglossal
- Movement of tongue (Motor)
9
Q
Compare and contrast the functions of the parasympathetic and sympathetic nervous systems.
A
- The autonomic nervous system is divided into the sympathetic and parasympathetic divisions.
- The sympathetic system prepares individuals for emergencies.
- This “fight or flight” response readies people to defend themselves or flee from danger.
- The skin becomes pale, secondary to the diversion of blood flow to more vital organs.
- Blood flow also decreases to structures such as external genitalia and abdominal organs.
- Thus, body processes such as digestion slow or stop, allowing more blood to flow to the brain, lungs, and large muscles that move the body during an emergency.
- Involuntary defecation or urination can occur.
- The parasympathetic system maintains body functions under normal conditions.
- The parasympathetic division maintains normal body functions and returns a person’s body to normal after a stressful situation.
- These opposing reactions (antagonism) maintain homeostasis.
10
Q
Explain nerve transmission, including definitions for resting potential, action potential, and neurotransmitter.
A
- Nerve Transmission
- Messages from one part of the body to another can take several possible nerve pathways.
- The body is thrifty in its use of resources and in patterns of automatic activities.
- Generally, it uses the quickest route to send a message.
- The body builds patterns (reflexes) and habits by using the same nerve pathways repeatedly.
- The same kind of message tends to follow the same path every time.
- Repeated motions become more or less automatic.
- Resting potential
- The electrical potential of a neuron or other excitable cell relative to its surroundings when not stimulated or involved in passage of an impulse.
- Action Potential
- The changed polarity of the neuron’s plasma membrane and the electrical impulse generated by ion movement.
- Neurotransmitters
- Are your body’s chemical messengers.
- They carry messages from one nerve cell across a space to the next nerve, muscle or gland cell.
- These messages help you move your limbs, feel sensations, keep your heart beating, and take in and respond to all information your body receives from other internal parts of your body and your environment.
11
Q
The __________ is the basic structural and functional cell of the nervous system.
A
Neuron
12
Q
A/An __________ is an extension that carries impulses away from the neuron cell body.
A
Axon
13
Q
__________ are short, often highly branched extensions of the cell body.
A
Dendrites
14
Q
__________ axons conduct impulses more rapidly than unmyelinated axons.
A
Myelinated
15
Q
A __________ is a chemical that an axon
releases to allow nerve impulses to cross the synapse and therefore reach the dendrites.
A
Neurotransmitter
