L5 Nervous System.pptx

ANATOMY & PHYSIOLOGYSEMESTER: 1WEEK NUMBER: 9LECTURE

CLAIRE BRADY

Anatomy & Physiology

OUTCOME

An appreciation of the CNS

An appreciation of the structure of the ANS


NERVOUS SYSTEM

Two subdivisions:• CNS: Central Nervous System

• Composed of the brain and spinal cord

• PNS: Peripheral Nervous System• Consists of nerves, ganglia,

cranial and spinal nerves

CENTRAL NERVOUS SYSTEM

Consists of two major organs• The brain and spinal cord

Protected by:• Brain = skull• Spinal cord = vertebral column

Brain & spinal cord are continuous and pass through an opening at the base of the skull

BRAINControl centre of the body

Protected by the skull (22 bones)

Three main parts:• The cerebrum

• The cerebellum• Brain Stem (Hypothalamus, Pons, Medulla Oblongata).


BRAIN


CEREBRUMLargest part of the brain

Consists of two hemispheres

Divided by a deep longitudinal fissure

Each cerebrum controls the opposite side

The outer layer: “Cortex” or “grey matter”

Inside the grey matter is white matter (nerve fibres)• Conscious part of brain• Allows us think and to voluntarily control our movements


LOBES OF EACH CEREBRAL HEMISPHERE

Each hemisphere has 5 lobes

1. Frontal – personality, behaviour, emotion, intelligence

2. Parietal – sensation, located on top

3. Occipital – vision, most posterior lobe

4. Temporal – controls hearing & smell – lateral aspect

5. Insula – deep within cerebral cortex. “Higher functions”

DIENCEPHALON- Upper end of the brain stem, between the cerebrum and the brain stem

Surrounded by cerebral hemisphere & includes the thalmus & the hypothalmus

Thalmus: relay station for sensory & motor signals to the cerebral cortex

HYPOTHALAMUSSituated deep within the cerebrum at the top of the brain stem

Pituitary gland attached to its base

Function:• Regulation of body temperature, water balance and metabolism

• Emotions (limbic system)

• Regulates the pituitary gland: main link between the nervous and endocrine systems

DIENCEPHALON


CEREBELLUMReferred to as the ‘small brain’

2nd largest portion of the brain

Functions: Motor area of the brain that regulates subconscious contractions of skeletal muscle

• Essential for co-ordination, posture, balance• If damaged – movements such as running, walking would be

uncoordinated

BRAIN STEMBetween the diencephalon & spinal cord

Consists of the midbrain, pons & medulla oblongata

Regulates activities essential to life:• Visual reflex centre• Auditory reflex centre• Respiratory control centre• Cardiac centre – regulates heart rate• Vasomotor centre to regulate blood pressure• Coughing, sneezing, vomiting, swallowing

PONS VAROLIIFrom the latin “bridge”

In front of the cerebellum and above the medulla oblongata

Consists of nerve fibres bridging gap between the two hemispheres of the cerebellum

Function: transmit messages to and from the spinal cord and the cerebrum

MEDULLA OBLONGATAThe medulla oblongata is smaller than the

cerebellum and is directly connected with the spinal cord

• Link from CNS to brain and vice versa

All sensory and motor nerves pass through this part of the brain

This area is also the origin of 10 of the 12 pairs of cranial nerves

It is also the centre of the autonomic nervous system which controls the heart, lungs, digestive system and other systems of the body


MEDULLA OBLONGATA

Functions:• Cardiac centre: controls rate and force of heart contraction

• Respiratory centre: controls rate and depth of breathing

• Vasomotor centre: controls constriction and dilation of blood vessels

• Reflex centre: responds to irritants thus controls vomiting, coughing, sneezing and swallowing.

SPINAL CORDExtends downwards through the vertebrae

Cylindrical in shape with an outer sheath enclosing cells and blood vessels

The inner core of the cord houses the nerve fibers

Extends to the first and second lumbar vertebrae

Consists of white matter on the surface and grey matter on the inside

Branches off into 31 pairs of spinal nerves


NERVES OF SPINAL CORD

Sensory nerves :• Afferent: Carry neural signals or impulses from sensory receptors

such as the skin, muscles and joints to the upper levels of the CNS

Motor nerves:• Efferent: Transmit messages or impulses from the brain and upper

spinal cord down to the end organs (muscles, glands etc)


PERIPHERAL NERVOUS SYSTEM

• Consists of nerves, ganglia, cranial and spinal nerves

• Ganglia = a collection of cell bodies outside of the brain, spinal cord & CNS

• 43 pairs of nerves▫ 12 pairs are cranial and they are connected with the brain▫ 31 pairs of spinal nerves and they branch off the spinal cord

• The spinal nerves directly supply the skeletal muscles of the body

• Nerves contain both sensory and motor neurons which transmit information to and from the body and the brain



Cranial Nerves • Most cranial nerves have a sensory & motor component

• Provide innervation to the head, neck, thorax & abdomen

• Come directly off the brain rather than the spinal cord

• Process information from nerve cells/neurons that either innervate muscles, glands/carry impulse from sensory areas

• Numbered continuously anterior to posterior according to their attachment to the brain


12 pairs of cranial nerves:

• Olfactory Facial• Optic Auditory• Occulomotor Glosspharyngeal• Trochlear Vagus• Abducent Hypoglossal• Trigemental Accessory

SPINAL NERVES31 Pairs: emerge laterally from the spinal cord

Named accordingly to the segment of the spinal cord they correspond with

Sensory and motor component• 8 Cervical (C1 – C8)• 12 Thoracic (T1 - T12)• 5 Lumbar (L1 – L5)• 5 Sacral (S1 – S5)• One coccygeal

Plexus: • Where main portions of nerves join together• Network/group of nerves

PLEXUSESCervical Plexus:

• Nerve supply to the skin and muscles of the neck, shoulder & diaphragm (C1-C4)

Brachial Plexus:• Innervates skin & muscles of the upper extremity (C5 – T1)• Located posterior & superior to the clavicle

Lumbosacral Plexus:• Innervates skin & muscles of the lower extremity, abdominal wall,

buttocks & genitalia (L1 – L5) & (S1 – S5)

NEURONSFunctional unit of the nervous system

Billions of neurons make up complex structure of the nervous system

The neuron should be seen as the road that links the various parts of the body within the sensory-motor network

It links the spinal cord and the various connective tissues of the body


NEURON

NEURONThe neuron is created so as to send messages in one direction only

They are several types of neurons in the body

Three types of neuron are of direct interest to us as S&C coaches and each is based on its function:

• Sensory• Motor • Inter


TYPES OF NEURONSSensory Neuron

Transmit impulses from receptors in connective tissue to the brain or spinal cord

Transmit signals of:• Pain• Temperature • Pressure sensations

From the receptor cells such as those located in the skin back into the CNS

Motor Neuron

Transmit signals or efferent nerve impulses from the brain or spinal cord to the effector sites in the connective tissue or glands

There are two types of motor neurons: Upper and Lower motorneurons

Inter NeuronTransmit impulses from one neuron to

another


EFFERENT SUBDIVISIONS

Motor division of the PNS is divided into the somatic & autonomic nervous system

Somatic• Supplies motor impulses to skeletal muscle such as skin, muscles &

conscious activities• = voluntary nervous system – able to control

Autonomic• Supplies motor impulses to the cardiac, smooth muscles, stomach, intestines

& moderates unconscious activities• = involuntary nervous system – unable to control• = visceral nervous system (internal organs)

AUTONOMIC SUBDIVISIONS

Sympathetic• Fight/flight

• Emergencies• Adrenalin

• “Agonist” – causes the action

Parasympathetic• Resting & response

• Calm system• Helps body to conserve energy

• “Antagonist” – does the opposite


EXAMPLE OF ANS: FIGHT OR FLIGHT

This is the body’s natural protective response that is triggered involuntarily when an immediate physical response is required:

• Natural ANS induced physiological response that occurs in the human body

The actual biological response is always present in some small degree


There is a natural stress response that prepares our body mentally and physically to either run or fight 'through' a situation

The response varies depending on the stress perception of the situation

• If our perception is great, then a greater response will occur

Failure to alleviate this build-up will see a level of distress as the stress was not released


RESPONSE 1. The heartbeat increases

2. As the heart rate increases, so does blood pressure

3. Breathing becomes more shallow and rapid

4. Adrenaline and other hormones are released into the blood stream

5. The liver releases stored sugar into the blood stream to meet the increased need for more energy to ensure survival


RESPONSE6. The pupils dilate to let more light and other senses become

heightened

7. Muscles generate tension, preparing for movement, either to fight or to run

8. Blood flow is constricted to the digestive organs

9. Blood flow increases to the brain and major organs

10. Blood flow increases to the major muscles


RESPONSE11. Blood flow is constricted to the extremities

12. The body perspires to cool itself

13. Blood clotting agents are released in anticipation of injury


COMPOSITION OF THE ANS

Sympathetic and Parasympathetic Systems

The main functions which are important to us as S&C specialists relate to:

• Heart rate control• Blood distribution management• Blood pressure control• Respiration• Emotional control• Hormonal control


SYMPATHETIC SYSTEM•Stimulation of the sympathetic system has the effect of

increasing body activity

•When the sympathetic system is dominant it increases:▫ Heart rate▫ Blood pressure▫ Blood glucose concentration▫ Metabolic rate▫ Sweat secretion▫ Blood vessel dilation▫ Bronchodilation in the airways▫ Mental activity▫ Renal and digestive systems are slowed down so as to conserve energy

that can be used elsewhere (reduced urge to urinate during exercise)


PARASYMPATHETIC SYSTEM

When the parasympathetic system is dominant it slows down body activity

• Slows heart rate• Lowers blood pressure• Decreases sweat secretion• Reduces metabolic rate• Reduces mental activity


The sympathetic system is stimulated by strong emotions such as anger and excitement

The adrenal glands are stimulated by the sympathetic system and secrete adrenaline

In some people the sympathetic system can be the dominant system in general and this means that they have a more frequent and higher than normal adrenaline releaseAnatomy & Physiology

ASSESSING THE ANS•Most common form is Heart Rate Variability▫ Heart rate variability is essentially the time period between heart

beats

•The interval is measured in milliseconds and each beat interval is then used and compared to establish the stress-recovery status of the athlete

•Typically, during exercise this interval is reduced and during rest it is increased


When an athlete is resting or is well recovered there is a good degree of variation in his or her time between beats

In contrast when the athlete is training or is stressed there is less variability – or more rigidity


THEORY BEHIND THE SYSTEM

The system involves indirect measurement of both the sympathetic and parasympathetic nervous systems

The theory is that by measuring the time interval parasympathetic drive is being determined

Thus heart rate variability or the variation in the time beats is used to assess the dominance or balance of these two systemsAnatomy & Physiology

Where the time interval varies a lot then the parasympathetic system is dominant

When the variation in heart beat is small the sympathetic system is dominant


REFERENCESCael, C. (2010) Functional Anatomy. Philadelphia: LWW

Arnould-Taylor, W. (2001) A textbook of Anatomy & Physiology. Cheltenham: Nelson Thornes.

Tucker, L. (2008) An introductory guide to A&P. Chapter 7.


L5 Nervous System.pptx

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