the nervous system Flashcards
What are the two parts of the nervous system?
- Central Nervous System
- Peripheral Nervous System
What does the peripheral NS divide into?
- The afferent NS (sensory)
- The efferent NS (motor)
What does the efferent NS divide into?
- The somatic NS (controlled)
- The autonomic NS (automatic)
What does the autonomic NS divide into?
- The sympathetic NS (fight or flight)
- The parasympathetic NS (rest & repair)
What does the central NS divide into?
- The brain
- The spinal cord
What are the parts of the brain?
- Cerebrum
- Cerebellum
- Brain stem
- Diencephalon
What are the parts of the brain stem?
- Medulla
- Pons
- Midbrain
What are the parts of the Diencephalon?
Thalamus
- Hypothalamus
- Epithalamus
What are the meninges?
inner protective covering of the brain and spinal cord (outer part of the brain)
What are the three layers of the meninges?
- Dura mater
- Arachnoid mater
- Pia mater
Describe the Dura mater.
- Outermost layer
- Strong white fibrous connective tissue
- forms inner periosteum of the cranial bones
Describe the Arachnoid mater.
- Delicate (cobweb like) middle ‘cushion’ layer
-Smooth - Cerebrospinal fluid in the subarachnoid space cushions the brain
Describe the Pia mater.
- Innermost transparent layer directly covering brain and spinal cord
- follows brain’s wrinkles
- has blood vessels- brain bleed
What are the three main meninges-related spaces?
- Epidural space
- Subdural space
- Subarachnoid space
Describe the epidural space
between dura matter and bony coverings in spinal cord- cushioning function with fat and connective tissue
Describe the subdural space
between dura mater and arachnoid mater- lubricating function with serous fluid
Describe the subarachnoid space
between arachnoid mater and pia mater- cushioning function with lots of cerebrospinal fluid
Where is cerebrospinal fluid made?
Choroid plexuses from blood plasma by ependymal cells
What is cerebrospinal fluid?
- Cushioning fluid protecting the brain and spinal cord
- found in subarachnoid spaces and cavities/canals
How much cerebrospinal fluid is there?
about 140ml
- 117 in subarachnoid spaces
- 23 in CSF ventricles
What does the cerebrospinal fluid monitor?
Change in the internal environment
- CO2 levels
- triggers hypothalamus
What does interference with CSF flow cause (tumor)
Build up of pressure on nervous tissue -> damage -> coma or death
What is the largest division of the brain?
The cerebrum (83% of brain mass)
Describe the cerebrum
- Largest brain division
- 4 lobes (5th small lobe)
- Has elevated ridges (gyri and sulci)
- White matter inside, grey outside
- Basal nuclei are deep inside
What is the function of the cerebrum?
- Sensory and motor functions
- 47-52 functional ‘Brodmann areas’ in the cortex
- touch, pressure, temperature, body position, vision, hearing, intelligence, learning, memory
What area of the brain is responsible for speech?
Broca’s area of the frontal lobe of the cerebrum
What is the left hemisphere of the cerebrum involved in?
language and gestures
What is the right hemisphere of the cerebrum involved in?
auditory stimuli (crying, laughing, music
Where is the diencephalon located?
Between the cerebrum and midbrain
What are three important structures of the diencephalon?
thalamus, hypothalamus, epithalamus
Describe the thalamus
- receives incoming sensory impulses
- regulates sleep (damage -> coma)
- Produces sensations and their associations
- arousal
What is the hypothalamus referred to as?
The survival and pleasure centre
What two systems does the hypothalamus connect?
Nervous and endocrine
What does the hypothalamus regulate?
- Homeostasis
- Alert state
- growth hormone secretion
(terrible if damaged)
What is the epithalamus?
Small structures outside the thalamus and hypothalamus
What are some areas of the epithalamus?
The pineal gland
- Regulates biological clock
- produces melatonin
The optic chiasma
- optic nerves cross and exchange fibres
Choroid plexuses
- CSF produced here
What is the pretectum?
A sub organ which receives input from eyes and controls pupillary light reflex (dilation)
What are the three divisions of the brain stem?
- Medulla Oblongata
- Pons
- Midbrain
Where is the medulla oblongata?
The lowermost part which joins with the spinal cord
What is the most vital part of the brain?
The medulla oblongata- injury or disease causes death
Where are the ‘vital centres’ located?
The vital centres (cardiac, vasomotor, respiratory), are located in the medulla oblongata.
What is the function of the medulla oblongata?
controls heart action, blood vessels, breathing, coughing, sneezing
Where is the pons located?
Between the midbrain and the medulla oblongata
What is the function of the pons?
- contains response centres for cranial nerves v,vI,VII,VIII
Where is the midbrain located?
Above the pons and below the cerebrum (middle of brain)
What does the midbrain contain?
- Auditory and visual centres
- clusters of neurons involved in muscular control
- centres for pupillary reflexes and eye movements
Where does the cerebellum lie?
Below the cerebrum
What part of the brain has the highest concentration of neurons?
The cerebellum
What are the functions of the cerebellum?
- produces skilled movement by coordinating groups of skeletal muscles
- Maintains muscle tone and posture
- Coordinates balance
- assists the cerebrum
What is the definition of meningitis?
Inflammation of the meninges- usually of the arachnoid and pia mater.
What are the symptoms of meningitis?
- fever
- severe headache
- neck pain
- photophobia
What is meningitis usually caused by?
Bacterial infection
What are some less likely causes of meningitis?
- Viral infections
- Tumors
What are some disorders of the CNS?
- Stroke (insufficient blood flow to neurons)
- Cerebral palsy (damage by trauma, infection, poisons, reduced oxygen to brain)- voluntary muscle control is impaired
- Dementia (Alzheimer’s)
- Prion related diseases
What does the autonomic nervous system do?
controls smooth muscle,
cardiac muscle and glands (“involuntary”)
what does efferent mean?
outgoing motor pathways exiting brain
What does afferent mean?
incoming sensory information from receptors
What does the somatic nervous system do?
controls skeletal muscles and
external sensory receptors (“voluntary”)
what are the two divisions of the autonomic nervous system?
- sympathetic (fight or flight)
- parasympathetic (R&R)
What does the central nervous system do?
-Integrates and evaluates incoming sensory information
- initiates outgoing responses
What does the peripheral nervous system consist of?
- 12 pairs of cranial nerves (origin brain)
- 31 pairs of spinal nerves (origin spine)
What does the peripheral nervous system divide into?
- Somatic
- Autonomic
What does the somatic nervous system control?
Skeletal muscles (voluntary)
What does the autonomic nervous system control?
Smooth muscle (cardiac and glands, involuntary)
What is the sympathetic division of the the autonomic nervous system?
‘fight or flight’ response
- expendble: wont die if severed
What is the parasympathetic division of the autonomic nervous system? and some functions
‘rest and repair’ response
- necessary to sustain life
- slows heart, stimulates salivary secretions,
What do neurons do?
conduct impulses
What are the parts of a neuron?
- Cell body
- axon
- dendrite
What do glial cells do?
- Support the function of neurons
- Isolate nerve fibres from one another
- Make up approx 50% of brain
why are glial cells unlike neurons?
They can divide throughout life
What are the types of glial cells?
- Astrocytes
- Microglia
- Ependymal Cells
- Oligodendrocytes
- Schwann cells
- Satellite cells
Name and describe 4 types of glial cells
Astrocytes
- most abundant
- feed neurons lactic acid from glucose
Oligodendrocytes
- hold nerve fibres together
- produce phospholipid myelin sheaths around axons in CNS
Schwann cells
- Equivalent of oligodendrocytes for the PNS
Satellite cells
- type of schwann cell
- surrounds cell bodies with ganglia in PNS
What is grey matter
Nerve tissue lacking myelin
What is white matter?
grouped bundles of myelinated axons in CNS
What is the peripheral nerve?
Bundle of myelinated axons that travel outside CNS
What is a tract?
A group of myelinated axons that travel together within CNS, share origin, destination, function
- similar to nerves but run entirely within CNS
What is a nucleus?
A group of neuronal cell bodies located in the same area and sharing the same function
What is a ganglion?
- similar to nuclei as also collections of neuronal cell bodies, but ganglion is outside CNS
What is multiple sclerosis?
A disease of the CNS which consists of myelin loss due to injured or dead oligodendrocytes. Symptoms are weakness, loss of coordination etc.
What are some peripheral nervous system disorders?
Acoustic neuroma:
- Lesion of Scwann cell sheath covering cranial nerve VIII
Multiple neurofibromatosis
- Benign Schwann cell nodules on skin