Nervous Tissue & The Brain Flashcards
What are the 2 subdivisions of the nervous system, and what do each include?
- central nervous system (CNS): includes the brain and spinal cord
- peripheral nervous system (PNS): includes the cranial nerves, spinal nerves, and ganglia
Name and describe the 3 general functions of the CNS and PNS.
- collecting information: receptors detect changes in the internal and external environment; pass info onto CNS
- processing and evaluating information: CNS determines the required response
- responding to information: CNS initiates nerve impulses to the effectors to react to changes in the body’s environment
What are the 2 types of cells within the nervous system? Describe each.
- neurons (nerve cells): electrically excitable cells that initiate, transmit, and receive nerve impulses
- glial cells: non excitable cells that support and protect the neurons
Name 3 special characteristics of neurons.
- high metabolic rate
- extreme longevity
- nonmitotic
What are the 3 main structural regions of a neuron?
- cell body
- dendrites
- axon
What are dendrites?
- short processes that branch from the cell body
- receive nerve impulses and carry them to the cell body
What do axons do?
transmit nerve impulses away from the cell body and transmit information to other cells
The region where the axon connects to the cell body is the ____ ______.
axon hillock
Glial cells are sometimes referred to as _______.
neuroglia
Where are glial cells found?
in both CNS and PNS
What is the function of glial cells?
physically protect and nourish neurons
How do glial cells differ from neurons?
- smaller than neurons
- capable of mitosis
- more numerous than neurons
- brain tumours are more likely to be derived from glial cells than neurons
Name and describe the function of the 4 types of glial cells in the CNS.
- astrocytes: bind blood vessels (nutrients) to neurons, form BBB
- ependymal cells: produce CSF
- microglial cells: immune response
- oligodendrocytes: generate myelin
Name and describe the function of the 2 types of glial cells in the PNS.
- satellite cells: protection, nutrients for cell bodies
- Schwann cells (neurolemmocytes): generate myelin
What is a synapse?
specialized junctions between one axon and another neuron, muscle cell, or gland cell
A typical synapse consists of ________, _________, and ______.
- presynaptic neuron
- postsynaptic neuron
- synaptic cleft
What are the 4 major regions of the brain?
- cerebrum
- diencephalon
- brainstem
- cerebellum
Describe gray matter.
- houses motor neuron and interneuron cell bodies, dendrites, unmyelinated axons
- forms the cortex, which covers the surface of most of the adult brain
- forms discrete internal clusters called cerebral nuclei
Describe white matter.
- made up of myelinated axons
- deep to the gray matter of the cortex
Name 4 structures that protect the brain.
- bony cranium
- protective connective tissue (meninges)
- CSF
- blood-brain barrier
What do the cranial meninges do?
- separate soft tissue of the brain from bones of cranium
- enclose and protect blood vessels that supply the brain
- contain and circulate CSF
- form some of the veins that drain blood from the brain
What are the layers of the cranial meninges?
- pia mater
- arachnoid mater
- dura mater
What are ventricles of the brain?
cavities within the brain that contain CSF
What are the 4 ventricles, and where are they found?
- 2 lateral ventricles: one in each hemisphere of cerebrum, separated by a thin septum pellucidum
- third ventricle: in dicephalon
- fourth ventricle: between pons and cerebellum
What does CSF stand for, and what is it?
- cerebrospinal fluid
- clear, colourless liquid that circulates in the ventricles and subarachnoid space
What are the functions of CSF?
- buoyancy: brain floats in the CSF
- protection: CSF provides liquid cushion
- environmental stability: CSF transports nutrients and removes waste from brain
Describe the cerebrum?
- the location of conscious thought processes and origin of intellectual functions
- contains a large number of neurons that are needed for complex analytical and integrative functions
- contains an outer cortex, inner white matter, and deep regions of gray matter called cerebral nuclei
- surface is marked by sulci, gyri, and deep grooves called fissures
The cerebrum is composed of two halves called left and right ______ _________.
cerebral hemispheres
The paired cerebral hemispheres are divided by a ________ _______ that extends along the _________ plane.
- longitudinal fissure
- midsagittal
What is the corpus callosum?
the largest tract and the main tract that connects the two hemispheres
Name the 5 lobes that each cerebral hemisphere is divided into.
- frontal lobe
- parietal lobe
- temporal lobe
- occipital lobe
- insula
Where is the frontal lobe located?
- deep to the frontal bone
- forms anterior part of the cerebral hemisphere
The frontal lobe is involved in what functions?
- voluntary motor functions
- concentration
- verbal communication
- decision making
- planning
- personality
Where is the parietal lobe located?
- forms the superoposteriar part of each hemisphere
- underlies parietal bone
The parietal lobe is involved in what functions?
general sensory functions
Where is the temporal lobe located?
- inferior to the lateral sulcus
- underlies temporal bone
The temporal lobe is involved in what functions?
- hearing
- smell
Where is the occipital lobe located?
- posterior region of each hemisphere
- underlies occipital bone
The occipital lobe is involved in what functions?
- processes incoming visual information
- stores visual memories
Where is the insula located?
deep to the lateral sulcus
The insula is involved in what functions?
- memory
- interpretation of taste
What are 3 components of the diencephalon?
- epithalamus
- thalamus
- hypothalamus
Where is the epithalamus located?
- partially forms posterior roof of diencephalon
- covers third ventricle
Name and describe 2 components of the epithalamus.
- pineal gland: secretes melatonin
- habenular nuclei: relay signals from the limbic system to the midbrain; involved in visceral and emotional responses to odour
What is melatonin?
a hormone that regulates circadian rhythm
What is the thalamus, and where is it located?
- paired oval masses of gray matter
- lie on each side of third ventricle
What are the functions of the thalamus?
- sensory impulses from all conscious senses except olfaction converge on the thalamus and synapse in at least one of its nuclei
- principal and final relay point for sensory information that will be processed
Where is the hypothalamus located?
anteroinferior region of the diencephalon
What is the infundibulum?
thin, stalk-like structure that extends inferiorly from hypothalamus to attach to pituitary gland
What are the functions of the hypothalamus?
- master control of the autonomic nervous system
- master control of the endocrine system
- regulation of body temperature
- control of emotional behaviour
- control of food intake
- control of water intake
- regulation of sleep-wake (circadian) rhythms
Describe the brainstem.
- connects prosencephalon and cerebellum to spinal cord
- passageway for all tracts extending between cerebrum and spinal cord
- contains many autonomic centres and reflex centres required for survival
- houses nuclei of many of the cranial nerves
What are the 3 regions of the brainstem?
- midbrain
- pons
- medulla oblongata
What does the cerebral aquaduct connect, and where is it found?
- ventricles
- midbrain
What are the functions of the midbrain?
- auditory reflex
- integration center (involuntary commands)
- produce dopamine
Where are the pons located?
bulging region on the anterior part of the brainstem
What are the functions of the pons?
- contains autonomic nuclei in the pontine respiratory centre, which helps regulate breathing
- receives auditory input and helps localize sound
The medulla oblongata contains several autonomic nuclei, which group to form what 4 things?
- cardiac centre: regulates heart rate and its strength of contraction
- vasomotor centre: controls blood pressure by regulating contraction and relaxation of smooth muscle in walls of arterioles
- medullary respiratory centre: regulates respiratory rate
- other nuclei involved in coughing, sneezing, salivation, swallowing, gagging, and vomiting
What are the functions of the cerebellum?
- coordinates and fine-tunes skeletal muscle movements
- stores memories of previously learned movement patterns
- adjusts skeletal muscle activity to maintain equilibrium and posture
- receives proprioceptive (sensory) information from the muscles and joints and uses this information to regulate the body’s position
- monitors the position of each body joint and its muscle tone
How many pairs of cranial nerves are there, and how are they named?
- 12 pairs
- numbered with Roman numerals by their position, beginning with the most anteriorly placed nerve
