Life Science - For exam! Flashcards
Glial Cells (Neuroglia)
Support communication work carried out by neurons.
Function of the Nervous System
Rapid communication system which coordinates and regulates body functions.
Anatomical Divisions of the Nervous System
- Central Nervous System (Brain and Spinal Cord)
2. Peripheral Nervous System (Cranial and Spinal Nerves)
Two Functional Divisions of the PNS
- Afferent (sensory)
2. Efferent (motor)
2 Divisions of the Efferent Division of the PNS
- Somatic (Voluntary)
2. Autonomic (Involuntary)
Functions of the Somatic Division of the PNS
Controls skeletal muscle contractions. Making a conscious choice to move your body.
Function of the Autonomic Division of the PNS
Subconscious control of motor functions. This includes reflexes, organs and body tissues not under conscious control (heart, etc.)
Controls the activity of smooth muscle such as the walls of airways or blood vessels, cardiac muscles and glands.
Functions of the Efferent Division of the PNS
Passes motor commands from the CNS to effector organs.
Functions of the Afferent Division of the PNS
Sends sensory data from sense organs to CNS.
Divisions of the Autonomic Nervous System
- Sympathetic (fight or flight)
2. Parasympatheic (resource storage and acquisition)
Function of Sympathetic Division of PNS
Responsible for mobilizing the body to deal with stressful situations. Fight or flight response. Predominates during stressful situations.
Function of Parasympathetic Division of PNS
Responsible for acquisition and storage of resources. Predominates when the body is at rest.
Four Anatomical Brain Parts
- Cerebrum
- Diencephalon
- Brain stem
- Cerebellum
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The Cerebrum
Largest structure of the human brain.
Divided into two cerebral hemispheres which control colateral sides of the body.
Structure of the Cerebrum
Contains folds (gyri), gaps (sulci) and larger gaps (fissures).
Contains two type of brain tissue: white matter and gray matter.
Gyri
Folds found in the cerebrum.
Sulci
Large gaps of space found in the cerebrum.
Fissures
Large gaps of space between gyri in the cerebrum.
Composition of Gray Matter
Composed mainly of neuron cell bodies.
Composition of White Matter
Composed mainly of neuron axons.
Cerebral Cortex Anatomy
Layer of gray matter on the surface of the cerebral hemispheres.
Function of the Cerebral Cortex
Receives sensory information, initiates and controls voluntary movement, site of higher functions including information processing, understanding, thinking, memory and personality.
Basal Ganglia
Small areas of gray matter located deep within the cerebral hemispheres.
Involved in fine control and regulation of voluntary movement.
Lobes of the Cerebral Hemisphere
- Frontal
- Parietal
- Occipital
- Temporal
Functions of the Frontal Lobe of the Cerebral Hemisphere
- Motor cortex and motor planning area
- Associated with higher functions including integrated thought, personality, motivation and regulation of emotional behavior and mood.
- Functional center for aggression.
LOCATIoN oF LOBES OF THE cEREBRAL HEMISPHERES
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Function of the Parietal Lobe
Receives sensory information from the body. Responsible for understanding speech and perception.
Function of the Occipital Lobe
Receives visual information from sensory organs.
Function of the Temporal Lobe
Receives auditory information from sensory organs.
Composition of the Diencephalon
Composed of the Thalamus and Hypothalamus.
Function and Anatomy of the Thalamus
- Comprises clusters of neurons.
- Acts as the main relay center for sensory information arriving in the brain.
- Begins the processing of sensory information and filters out unimportant information before routing significant signals to the cerebral cortex.
- Plays and important role in voluntary movement.
Function and Anatomy of the Hypothalamus
- Lies beneath the thalamus.
- Physically connected to the pituitary gland.
- Made up of a large number of clusters of which carry out the functions of the hypothalamus.
- Responsible for regulation of sleep and wake cycles, appetite, thirst, water balance, sexual behavior, body temperature.
- Controls the Autonomic Nervous System.
Structures of the Brain Stem
- Medulla Oblongata
- Pons
- Midbrain
Medulla Oblongata
An enlarged upright extension of the spinal cord.
Pons
Connects the cerebral cortex with the medulla oblongata.
It also serves as a communications and coordination center between the two hemispheres of the brain. As a part of the brainstem, the pons helps in the transferring of messages between various parts of the brain and the spinal cord.
Midbrain
Acts as a relay information system for the auditory, visual, and motor systems of the body.
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Reticular Formation
Small clusters (nuclei) of gray matter scattered throughout the brain stem.
The neurons of the reticular formation receive sensory input from a wide range of sources and the cerebral cortex and cardiovascular and respiratory systems.
Function of the Brain Stem
Functions as a two way conduction system. Sensory pathways conduct signals up from the spinal cord to the rest of the brain. Motor pathways conduct signals down from the brain to the spinal cord. Some nerve fibres pass through, most actually synapse in the brain stem.
Tissue of the Brain Stem
Consists mainly of white matter with small clusters of grey matter (nuclei) scattered throughout.
Where do most nerve signals synapse?
In the brain stem
Reticular Activating System (RAS)
Arouses and maintains consciousness.
Stimulation of RAS nerves maintains alertness and attention (ie. bright lights, loud noise or noxious smells arouse consciousness)
How do general anesthetics function?
By suppressing the reticular activating system (RAS).
How is clinical brain death established?
Through a lack of electrical activity in the brain stem.
Vital centers in the brain stem
- Cardiovascular center
- Respiratory Center
- Reflex centers
Cardiovascular Center of the Brain Stem
Controls the rate and force of contraction of the heart.
Also contained the vasomotor center which controls diameter of blood vessels.
Respiratory Center of the Brain Stem
Controls the rate and depth of breathing. Functions in association with similar nuclei in the pons.
Reflex Center of the Brain Stem
Activated by irritants to the airways or stomach which activate reflex centers in the medulla to induce coughing, vomiting, or sneezing to remove the irritant.
Swallowing and blinking reflexes are also associated with the medulla.
Decussation of the Pyramids
Motor nerve axons descending from the cortex to the spinal cord which cross over in the medulla.
This accounts for the contralateral effect of the cerebrum controlling the opposite side of the body.
Function of the Cerebellum
To coordinate voluntary movement, posture, balance and motor learning. Ensures smooth fluid body movement. It receives sensory information from voluntary muscles, eyes and ears.
Proprioception
Information received from the body enables the cerebellum to determine where the limbs are in relation to the rest of the body; the eyes and ears provide information on where the head is in space.
How does the cerebellum maintain posture and balance?
Through sensory information received through proprioception.
Damage to the cerebellum
Causes uncoordinated, clumsy movement and staggering. May also cause inability to learn new complex movement.
Spinal Cord
A column of nerve tissue carrying sensory information to the brain and motor information from the brain.
Also responsible for certain reflexes.
How many spinal nerves are there?
31 pairs of spinal nerves
What types of spinal nerves are there?
8 pairs - cervical 12 pairs - thoracic 5 pairs - lumbar 5 pairs - sacral 1 pair - coccygeal
Nerves in the spinal cord
Nerves enter and leave the spinal cord through spinal nerves.
Sensory nerves enter by the dorsal root.
Motor nerves leave by the ventral root.
Dorsal Root
Sensory nerves enter the spinal cord through this root.
Ventral root
Motor nerves leave the spinal cord through this root.
Sensory Nerve Pathway
Sensory information travels to the cerebral cortex by a three neuron pathway crossing over to the contralateral side of the brain.
- Posterior column
- Anterior and lateral spinothalmic tracts
- Spinocerebellar tract.
First, second, and third order neurons
First order - carry signal from the sense organ to the spinal cord.
Second order - relays information from the spinal cord to the thalamus.
Third order - Transmit information from the thalamus to the primary sensory cortex where the information is processed.
Motor Nerve Pathways
Motor commands travel from the cerebral cortex by direct or pyramidal pathway which involves two neurons (upper and lower motor neurons).
Decussation passes the signal to the opposite side of the body.
Major Motor Nerve Tracts
Anterior and Lateral corticospinal and corticobulbar tracts.
Spinal Reflexes
A movement which involves no command from the brain.
Function is mainly protective.
Sensory receptors send an action potential to an association or interneuron in the spinal cord which stimulates a motor neuron signaling a reflex muscle contraction.
Examples of spinal reflexes
- Patellar reflex
- Plantar flexion reflex
- Withdrawal reflex
Protection for the Central Nervous System
Provided by bone, meninges (protective, three layer membrane), and cerebrospinal fluid (CSF).
Meninges
A protective membrane for the central nervous system. Made up of three layers:
- Dura Mater (top)
- Arachnoid (middle)
- Pia Mater (bottom)