Chapter 4 - Central Nervous System Flashcards
What is the nervous system?
A communication network and control centre of the body and is made up of the brain, spinal cord and nerve.
What is the basic stricture of the nervous system?
- The central nervous system (CNS)
- consist of the brain and spinal cord - The peripheral nervous system (PNS)
- made up of nerves that connect the CNS with the RECEPTORS, MUSCLES, AND GLANDS
these all work together in a coordinated way.
What is the main job of the CNS?
The central nervous system is where incoming messages and processed and outgoing messages are initated.
Why should the CNS be protected?
The brain and spinal cord are very delicate and vital parts of the body. Therefore it is important that they are protected.
What three things protect the CNS?
- BONES - cranium and vertebrae
- Membranes called MENINGES
- CEREBROSPINAL FLUID
+ A CAVITY OF SPACE
How does the Cranium protect the brain?
It is the OUTERMOST PROTECTIVE LAYER OF THE BRAIN IS THE CRANIUM.
The cranium protects the brain by housing it in its STRONG, RIGID, AND HARD bone structure.
How does the Vertebrae protect the spinal cord?
The spinal cord runs the vertebral canal - an opening in the vertebrae.
THESE BONES PROVIDE A STRONG, RIGID STRUCTURE TO PROTECT THE STRUCTURES UNDERNEATH.
What are Meninges? and their location.
Meninges are the 3 layers of connective tissue forming into membranes covering the spinal cord and brain.
Located: Inside the bones covering the surface of the brain and the spinal cord (i.e CNS)
List the three layers of Meninges.
- Dura mater
- Arachnoid mater
- Pia mater
What is the Dura Mater?
- the outer meningeal layer
- tough and fibrous providing a LAYER OF PROTECTION for the brain
- STICKS CLOSELY to the BONES OF THE SKULL but on the INSIDE of the VERTEBRAL CANAL, it is NOT SO CLOSE FITTING.
- OUTER MEMBRANE has been DESCRIBED as having a TEXTURE AND THICKNESS SIMILAR to a HOUSEHOLD RUBBER GLOVE.
What is the Arachnoid mater?
Middle meningeal layer
- LOOSE MESH OF FIBRES
What is the Pia mater?
The INNER meningeal layer
- More DELICATE
- Contains many BLOOD VESSELS and STICKS CLOSELY to the SURFACE OF THE BRAIN AND SPINAL CORD.
What is the Cerebrospinal fluid? AND WHERE IS IT FOUND?
CSF is the third protective structure
- IS A CLEAR, WATERY FLUID CONTAINING FEW CELLS AND SOME
- GLUCOSE, PROTEIN, UREA AND SALTS
- OCCUPIES a SPACE BETWEEN THE MIDDLE AND INNER LAYERS OF THE MENINGES.
- CIRCULATES THROUGH CAVITIES IN THE BRAIN AND THROUGH A CANAL IN THE CENTRE OF THE SPINAL CORD.
has 3 functions
What are the three functions of the CSF?
- PROTECTION:
- acts as a shock absorber, cushioning any blows or shocks to the CNS may sustain - SUPPORT:
- the brain is suspended inside the cranium and floats in the fluid that surrounds it - TRANSPORT:
- the CSF is FORMED FROM BLOOD and CIRCULATES AROUND and THROUGH the CNS before RE-ENTERING the blood CAPILLARIES.
- DURING its CIRCULATION it TAKES NUTRIENTS TO the CELLS of the BRAIN and SPINAL CORD and CARRIES AWAY their WASTES
What is the brain?
Complex organ - in structure and function.
Works as an integrated whole.
not completely discovered: is still a mystery and discoveries still happening today
List the major regions of the brain which major functions
- Cerebrum
- Corpus Callosum
- Cerebellum
- Hypothalamus
- Medulla Oblongata
What is the Cerebrum? STRUCTURE
- the biggest part of the brain
- outer surface area of 2-4mm thick of grey matter known as the CEREBRAL CORTEX
- GREY MATTER CONSISTS OF NEURON CELL BODIES, DENDRITES, AND UNMYELINATED AXONS.
BELOW THE CORTEX is WHITE MATTER, which is made up of MYELINATED AXONS.
DEEP INSIDE THE CEREBRUM IS ADDITIONAL GREY MATTER CALLED THE BASAL GANGLIA.
WHITE MATTER VS. GREY MATTER
WHITE MATTER = the part of the brain and spinal cord made up of myelinated fibers.
- the fatty nature of the myelin gives the white matter its colour and texture
GREY MATTER= the part of the brain and spinal cord made up of nerve cell bodies and unmyelinated fibres
What is the basal ganglia?
The masses of grey matter inside each cerebral hemisphere
Explain the structure of the Cerebral cortex
- is folded in patterns that greatly increase the surface area.
- in this way the cortex 70% of all neurons in the central nervous system
- folding produced rounded ridges called CONVOLUTIONS (varying from person to person)
- the convolutions are separated by either SHALLOW DOWNFOLDS CALLED SULCI OR DEEP DOWNFOLDS CALLED FISSURES.
What are convolutions?
an UPWARD FOLD of the cerebral cortex of the brain
aka - gyrus
What are Sulci?
SHALLOW DOWNFOLDS between the convolutions of the cerebral cortex
singular sulcus
What are fissures?
A DEEP DOWNFOLD in the cerebral cortex of the brain
What is the cerebral hemisphere?
One of the 2 halves of the cerebrum
What is the longitudinal fissure? what joins it?
The longest fissure in the human brain:
- almost separates the cerebrum into 2 halves
- considered a fifth lobe of each cerebral hemisphere
joining the 2 hemispheres, at the base of the longitudinal fissure is an area of white matter consisting of a large bundle of transverse fibres known as the corpus callosum.
Certain fissures and sulci are constant and are used to further subdivide each cerebral hemisphere into 4 lobes.
What are the four lobes?
- Frontal lobe
- Parietal lobe
- Temporal lobe
- Occipital
*5. Insula
Certain fissures and sulci are constant and are used to further subdivide each cerebral hemisphere into 4 lobes.
What is the insula? and where is it located?
Part of the cerebrum, deep inside the brain and is regarded as a fifth lobe.
function: recognition of different senses and emotions, addiction and psychiatric disorders
What is the function of the frontal lobe?
Thinking, problem-solving, emotions, personality, language, and control of movement.
What is the function of the parietal lobe?
Processing temperature, touch, taste, pain, and movement.
What is the function of the temporal lobe?
Processing memories and linking them with senses receive auditory information.
What is the function of the Occipital lobe?
Vision
What is the function is of the cerebral cortex?
- Higher-order functions such as thinking, reasoning, memory, learning, conscious awareness of surroundings/responsibilities.
- Concerned with the PERCEPTION OF SENSES and the INITIATION AND CONTROL of VOLUNTARY MUSCLE CONTRACTION.
- Receives all impulses from sense organs, contains that information about the environment, and can initiate responses accordingly.
The cerebral cortex can be roughly divided into 3 functional areas. What are they?
- Sensory areas - which interpret impulses from receptors
- Motor areas, which controls muscular movements
- Association areas, concerned with intellectual and emotional processes. eg Memory.
Explain how memory is stored in the cerebral cortex.
The association areas of the cerebral cortex and involved in memory.
Not stored in individual memory cells in the brain: they are pathways of nerve cells
When a memory is stored, new links are made between neurons, or existing links are modified.
What are the differences between the left and right side of the brain and explain with an example.
- Either (2) sides of the cerebrum appear similar, however, they are not identical
Right-handed people: frontal lobe is wider than the left, the left occipital and parietal are wider than the right ones. - Many specialized functions occur only in one hemisphere.
- language ability controlled by the left
- musical and artistic abilities are functions of the right hemisphere
Where can the white matter be found in the brain?
located between the cerebral cortex and basal ganglia is white matter composed of bundles of nerve fibres that are surrounded by a sheath of white fatty material called myelin.
What are tracts?
Within then CNS, bundles of nerve fibres are called tracts
*outside the CNS they are called nerves
What are the three types of tracts that occur inside the white matter?
- Tracts that connect various areas of the cortex within the same hemisphere
- tracts that carry impulses between the left and right hemispheres
- tracts that connect the cortex to other parts of the brain or to the spinal cord.
What does the basal ganglia consist of?
groups of nerve cell bodies associated with control of skeletal muscles.
they play a role in initiating desired movements and inhibiting unwanted movement.
What is the corpus callosum? location and function?
what is it: a wide band of nerve fibres
location: lies underneath the cerebrum at the base of the longitudinal fissure.
Function: nerve fibres in the corpus callosum cross from one cerebral hemisphere to the other and allow the two sides to COMMUNICATE which each other.
What is the cerebellum?
location: LIES UNDER the REAR part of the cerebrum
2nd largest part of the brain
Structure: the surface is highly folded in a series-parallel ridge.
- outer folded part is grey matter
- inner portion is made up of white matter that branches to all the parts of the brain
The function: exercises control over POSTURE, BALANCE, FINE COORDINATION OF VOLUNTARY MUSCLE MOVEMENT
To carry out the cerebellum’s functions, where does it receive its sensory information from?
- the inner ear for the information about posture and balance
- stretch receptors in the skeletal muscles for information about the length of muscles
Do we need the cerebellum?
All functions take place BELOW CONSCIOUS LEVEL
- IMPULSES DO NOT ORIGINATE FROM IT, so, therefore, we can still move, but it would be SPASMODIC, jerky, and uncontrolled.
- Smooth, coordinated movements eg writing, playing an instrument, or using a computer would be impossible.
What is the hypothalamus? LOCATION, MAIN FUNCTION
Location: middle of the brain and cannot be seen from the outside
MAIN Functions: controls bodily activities, however, is concerned with MAINTAINING HOMEOSTASIS
List out the functions of the Hypothalamus (7)
REGULATION OF:
- AUTONOMIC NERVOUS SYSTEM, (heart rate, blood pressure, secretion of digestive juices, movement of the alimentary canal, the diameter of the pupil of the eye.)
- Body temperature
- Food and water intake
- patterns of waking and sleeping
- contraction of the urinary bladder
- emotional responses - fear,anger,aggression,pleasure,conetnement
- SECRETION OF HORMONES, and COORDINATION of parts of the ENDOCRINE SYSTEM: acting through the pit. gland, the hypothalamus regulates METABOLISM, GROWTH, REPRODUCTION, AND STRESS RESPONSE
What is the Medulla Oblongata? location and function
It is the continuation of the spinal cord.
-3cm long,
LOCATION: EXTENDS from the just ABOVE the POINT WHERE THE SPINAL CORD ENTERS THE SKULL
Function:
- many fibres simply pass through the medulla going to or from the other parts of the brain
- automatically adjusting body functions.
What does the medulla oblongata contain and their jobs which adjust body functions? What influences them?
ALL CENTRES are influenced and controlled by HIGHER CENTRES IN THE BRAIN, PARTICULAR HYPOTHALAMUS.
- CARDIAC CENTRE - regulates heart rate and force of the heartbeat
- RESPIRATORY CENTER - control rate and depth of breathing
- VASOMETRE CENTER - regulates the diameter of the blood vessels
- other centers regulate, REFLEXES OF SWALLOWING, SNEEZING, COUGHING, AND VOMITING.
What is the spinal cord? What? Location? Function
WHAT? The roughly cylindrical structure, about 44cm in adults.
LOCATION: extends from the FORAMNE MAGNUM (large opening at the base of the skull) – SECOND LUMBAR VERTEBRA (approx waist level)
FUNCTION:
1. carry sensory impulses to the brain, and motor impulses down from the brain
- integrate fast, automatic responses called reflexes
How is the spinal cord protected?
- the cord is enclosed in the VERTEBRAL CANAL (RING OF BONE)
- 3x MENINGEAL LAYERS, however, the outermost meningeal layer is not joined to the bone
- instead, a SPACE CONTAINING FAT, CONNECTIVE TISSUE, and BLOOD VESSELS serves as a PADDING around the spinal cord and allows the cord to BEND when the spine is bent.
How is the Spinal cord arranged?
- GREY MATTER is at the centre - H shaped
- WHITE MATTER surrounds it - nerve fibres are arranged in bundles known as ascending and descending tracts
- CENTRAL CANAL - small space in the middle which runs the length of the spinal cord and contains CSF
ASCENDING vs DESCENDING TRACTS
ASCENDING TRACTS - contains sensory axons that carry impulses upward - towards the brain
DESCENDING TRACTS - contains motor axons that conduct impulses downwards, away from the brain
What is the peripheral nervous system and what is it composed of?
PNS takes messages from receptors to the CNS and from the CNS to the muscles and glands
COMPOSED OF:
1. nerve fibres that carry information to and from the CNS
- GANGLIA (GROUPS OF NERVE CELLS) which lie outside the brain and spinal cord
What are the two types of nerves?
Nerve fibres arranged into nerves, which arise from the brain and spinal cord
- CRANIAL NERVES
- SPINAL NERVES
What are Cranial nerves?
- 12 PAIRS OF NERVES ARISING FROM THE BRAIN
eg optic and auditory - MOST are MIXED NERVES: they contain fibres that carry impulses into the brain and fibres that carry impulses away from the brain
- a few cranial nerves carry only sensory impulses or only motor impulses
SENSORY FIBRES VS MOTOR FIBRES
SENSORY FIBRES - fibres that carry impulses into the CNS
MOTOR FIBRES - carry impulses away from the CNS
What are SPINAL NERVES?
- 31 PAIRS OF NERVES ARISING FROM THE SPINAL CORD
- MIXED NERVES; containing both sensory and motor fibers
- each nerve is joined to the spinal cord by 2 roots
1. VENTRAL ROOT
2. DORSAL ROOT
DORSAL VS VENTRAL ROOT (DORSAL ROOT GANGLION?)
VENTRAL ROOT - contains axons of the MOTOR NEURONS THAT HAVE THEIR CELL BODIES IN THE GREY MATTER OF THE S.C.
DORSAL ROOT - contains axons of SENSORY NEURONS THAT HAVE ALL THEIR CELL BODIES IN A SMALL SWELLING.
DORSAL ROOT GANGLION? - SMALL SWELLING ON THE DORSAL ROOT
What are the different divisions of the PNS?
Since it contains nerve fibres from all over the body, it divided and subdivided into parts which a particular function called
- AFFERENT DIVISION
- EFFERENT DIVISION
WHAT IS THE AFFERENT DIVISION?
SENSORY division of the PNS
- HAS FIBERS that carry impulses INTO the CNS by SENSORY NEURONS from RECEPTORS IN THE SKIN, AROUND MUSCLE, AND JOINTS.
Can be further divided into SOMATIC SENSORY NEURONS AND VISCERAL SENSORY SENSORY NEURONS
SOMATIC SENSORY NEURON VS VISCERAL SENSORY NEURONS?
SOMATIC SENSORY NEURONS = bring impulses from the skin and muscles
VISCERAL SENSORY NEURONS = bring impulses from the internal organs
What is the efferent division?
MOTOR DIVSION which has fibres that carry IMPULSES AWAY FROM THE CNS
SUBDIVIDED INTO SOMATIC, AND AUTONOMIC
SOMATIC VS AUTONOMIC DIVISION
SOMATIC DIVISION AKA SOMATIC NERVOUS SYSTEM
- takes impulses from the CNS to SKELETAL MUSCLES
AUTONOMIC AKA AUTONOMIC NERVOUS SYSTEM, carries impulses from the CNS to the HEART, INVOLUNTARY MUSCLES, AND GLANDS.
- further divided into SYMPATHETIC AND PARASYMPATHETIC DIVISIONS
Explain the Autonomic Nervous system:
WHAT, OPERATES, REGULATES, AND WHAT REGULATES IT
(ANS)
Controls the body’s INTERNAL ENVIRONMENT and is involved in many of the MECHANISMS that keep it CONSTANT.
- OPERATES UNCONSCIOUS CONTROL
- REGULATED by GROUPS OF NERVE CELLS in the MEDULLA OBLONGATA, HYPOTHALAMUS, CEREBRAL CORTEX
SOME BODY FUNCTIONS regulated by it is
- heart rate
- blood pressure
- body temp
- digestion
- release of energy
- pupil diameter
- airflow to the lungs
- defecation
- urination
HOW DOES THE AUTONOMIC NERVOUS SYSTEM RELAY MESSAGES?
- nerve fibers of the ANS make up part of the SPINAL NERVES
- and some part of the CRANIAL NERVES
- nerve fibers of the ANS make up part of the SPINAL NERVES
- CARRIES IMPULSES TO THE HEART MUSCLE, OTHER MUSCLE OF THE INTERNAL ORGANS, and the GLANDS
- IMPULSE TRAVELS ALONG 2 NEURONS FROM THE CNS to an ORGAN CONTROLLED BY THE ANS
- FIRST NEURON IS MYELATED and it has CELL BODY IN THE CNS
- THE SECOND NEURON IS UNMYELATED and it has a CELL BODY in a GANGLION (pl. ganglia): a group of nerve cell bodies outside the CNS
Difference between the autonomic and somatic nervous systems?
(effectors, general function, effort pathways, neurotransmitter as effector, control what, nerve to the target organ, effect on target organs)
EFFECTORS
AUTONOMIC = HEART MUSCLE, INVOLUNTARY MUSCLE, AND GLANDS
SOMATIC = INVOLUNTRAY MUSCLES
GENERAL FUNCTION
AUTONOMIC = adjustment of the internal environment ( homestasis)
SOMATIC = response to external enviroment
EFFERENT (outward) PATHWAYS
AUTONOMIC = 2 nerve fibers from the CNS to the effector with a SYNAPSE AND A GANGLION
SOMATIC = ONE nerve fiber from the CNS to the effector, NO SYNAPSE OR GANGLION
NEUROTRANSMITTER AS EFFECTOR
AUTONOMIC = acetylocholine and noradrenaline
SOMATIC = actelylocholine
CONTROLs what?
AUTO - usually involuntary
SOMATIC - usually voluntary
NERVES TO TARGET ORGAN
AUTO = 2 SETS - sympathetic and parasympathetic
SOMATIC - one set
EFFECT ON TARGET ORGAN
AUTO - excitation, and inhibition
SOMATIC - ALWAYS excitation
SYMPATHETIC VS PARASYMPATHETIC divisions
SYMPATHETIC DIVISION
- TENDS to produce responses that prepare the body for STRENUOUS PHYSICAL ACTIVITY
PARASYMPATHTIC DIVISION
- produces responses that maintain the body at relatively QUIET CONDITIONS
The message from the autonomic nervous system nerves to the muscles/glands under their control is carried by what?
The message from the autonomic nervous system nerves to the muscles/glands under their control is carried by a neurotransmitter at the nerve endings.
parasympathetic - acetylcholine
sympathetic - noradrenaline
Normal circumstance regulated by the autonomic nervous system?
Maintain the stability of bodily functions.
eg. heart has an inbuilt rate of contraction of about 100 beats per minute.
while at rest the parasympathetic stimulation keeps it down to around 70-80 beast per minute.
Fight or flight reactions
Alarm reactions
SITUATIONS THAT INVOLVE FEAR, DANGER, ANGER, COMPETITION, OR STRESS INVOKE THIS RESPONSE.
Prepares the body to flee or fight; increased activity
therefore relies on SKELETAL MUSCLES PRODUCING MOVEMENT AND INCREASED LEVELS OF ALTERNESS TO THINK/ACT QUICKLY.
NEEDS INCREASED SUPPLY OF OXYGEN AND GLUCOSE, INCREASED BLOOD FLOW.
SYMPATHETIC DIVSION SHOWS DOMINANCE HERE.
EFFECTS OF SYMPATHETIC AND PARASYMPATHETIC STIMULATION ON DIFFERENT STRUCTURES
HEART
- increase/decrease rate and strength of contraction
LUNGS
- dilates/constricts bronchioles
STOMACH/INTESTINES
- Decrease/increase movement
LIVER
- increase/decrease breakdown of glycogen and release of glucose
IRIS OF THE EYE
-dilate/constrict the pupil
SWEAT GLANDS
-increase/decrease sweat secretion
Salivary Glands
- decrease/increase secretion of saliva
BLOOD VESSELS OF SKIN - CONSTRICTS OR LITTLE EFFECT BLD VESSELS OF SKELETAL MUSCLES -DILATES OR NO EFFECT BLD VESSELS OF INTERNAL ORGANS - CONSTRICT (EXCEPT IN HEART AND LUNG) OR LITTLE EFFECT
ADRENAL MEDULLA
- STIMULATES HORMONE SECRETION OR NO EFFECT
