A.1.1.1 - Nervous system (full)

Nervous system - Somatic

Voluntary control of skeletal muscles

Nervous system

Made up of neurons, specialised cells transmit chemical and electrical impulses throughout body

Nervous system allows for:

Communication, coordination and interaction of:

- Tissues within body

- Systems within body

- Between the body and external environment

Nervous system - CNS

Brain + spinal cord

- Brain acts as central processing computer for both conscious and unconscious activity

- Processes sensory info

Nervous system - PNS

All nerves outside CNS

Nervous system - Afferent

Sensory nervous system

- BODY -> BRAIN

- Informs CNS about external and internal conditions

Nervous system - Efferent

Motor nervous system

- BRAIN -> BODY

- Motor nerves send info from CNS to body systems

Nervous system - Autonomic

Involuntary movements

Nervous system - Parasympathetic

Rest + digest

- Helps body to regenerate

- Contributes to maintenance of homeostasis

3 Main function of the nervous system

1. Sensory function - stimuli detection

2. Integrative function - analysing and storing sensory info to make decisions

3. Motor responses

Nervous system - Sympathetic

Fight/flight

- Helps body respond to stressful stimulus

Nervous system - Examples of parasympathetic

- Decreases rates of heart muscle contractions to decrease strain on body

- Increased vasoconstriction of coronary blood vessels to decrease blood pressure

- Peristalsis (digestion) to increased digestion and absorption of nutrients

Nervous system - Examples of sympathetic

- Increased heartrate and strength of contraction in order to increase cardiac output

- Increased glucose from liver to blood to increase energy availability

- Vasodilation in active tissues to increase blood flow

Brain - 4 key components

1. Cerebellum

2. Cerebrum

3. Diencephalon

4. Brain stem

Brain - Brain stem

- Connects brain to spinal cord

- Carry motor and sensory messages through brainstem

- Respiratory and cardiovascular control centres

- Medulla oblongata, pons and midbrain

Brain - Cerebellum

- Helps smooth and coordinate skeletal muscle contractions, fluidity

- Regulates posture and balance

- Makes possible to learn skilled motor activities

- Coordinates eye movement

Brain - Cerebrum

- Conscious brain

- Composed of two connected hemispheres that communicate w each other

- Enables decision making, process sensory input, skilled and controlled movement

Brain - 4 components of cerebral cortex

- Frontal lobe: decision making, emotion, problem solving

- Parietal lobe: Spatial awareness, body positioning

- Temporal lobe: Language comprehension

- Occipital lobe: visual interpretation

Brain - Diencephalon

- Control centre for autonomic nervous system

- Contains thalamus and hypothalamus

Brain - Thalamus

- Acts as relay centre, sends sensory info to brain

- Coordinates motor responses

Brain - Hypothalamus

- Control centre for homeostasis

- Controls autonomic nervous system

Heart - Left side of the heart

- Blood from lungs

- Oxygenated

- Pumped to body via arteries

- Thicker artery walls

- Left atrium receives reoxygenated blood

- Left ventricle pumps out reoxygenated blood

Heart - Right side of the heart

- Blood returns from body

- Arrives through veins

- Deoxygenated

- Pumped to lungs

- Right atrium receives de-oxygenated blood

Pumped to be oxygenated by right ventricle

Heart - Ventricle

Large discharging chambers

Heart - Left ventricle

- Pumps blood to body

- More muscular

Heart - Right ventricle

- Pumps blood to lungs

Heart - Vein

Goes into heart (remember veins are blue, carry deoxygenated blood)

Heart - Artery

Goes away from heart

Heart - Aorta

- Largest artery in your body

- High elasticity

Heart - Superior vena cava

Brings in blood form above the heart

Heart - Inferior vena cava

Brings in blood from below the heart

Heart - Pulmonary artery

Transports deoxygenated blood from heart to lungs for oxygenation

Heart - Pulmonary veins

To bring blood back from lungs to heart - carries oxygenated blood

Heart - Atrium

- Smaller receiving chamber

- Fills with blood

- Contracts to push blood out

- Into relaxed ventricles

Heart - Valves

- Prevents incorrect direction of the blood flow

- Held in place by chordae tendinea

Heart - Cycle of circulation

1. Deoxygenated blood from body returns to heart via vena cava

2. Blood enter right atrium -> through tricuspid valve

3. Blood enters right ventricle -> pumped through pulmonary valve to pulmonary artery

4. Travels to lungs for gas exchange

5. Oxygenated blood returns to heart via pulmonary veins into the left atrium

6. Passes through the bicuspid valve into the left ventricle

7. Pumped into aortic valve into aorta then distributed

Heart - Spontaneous rhythmicity

- Hearts own electrical signal

- Doesn't require external nerve impulses to beat

- Comes from nodes rather than a motor neuron

Heart - Pathway of electrical impulse during the excitation of the heart

1. Electrical impulse generated at SA node

2. Impulse travels across atria walls, exciting tissue

3. Impulse arrives at AV node

4. Passes from AV node to bundle of HIS

5. Passes through left and right bundles to apex of heart

6. Travels through Purkinje fibres (spread along ventricle walls to stimulate rest of ventricles)

7. Ventricles contract and force blood out through main arteries

Heart - 3 factors of extrinsic excitation

1. Parasympathetic nervous system (slows down)

2. Sympathetic nervous system (speeds up)

3. Endocrine system (hormones released to stimulate heart force and rate)

Motor response - How to coordinate

SENSORY AND MOTOR SYSTEMS MUST INTERCOMMUNICATE

1. Sensory stimulus is received

2. Information travels along afferent nerves to CNS

3. CNS selects appropriate response

4. Response signal travels from CNS -> Efferent neurons

5. Motor response occurs

Motor response - Spinal cord

Reflex

- e.g. pulling finger away from hot surface

Motor response - brain stem

Subconscious

- e.g. postural control

Motor response - cerebellum

Coordination

- e.g. contracting muscle groups to perform desired movement

Motor response - thalamus

Consciousness

- Distinguishing between various sensations

Motor response - cerebral cortex

Location of sensory input from skin, muscles and tendons

- e.g. knowing where body parts are

Motor response - Sensory stimulation

- Travels along sensory nerves to spinal cord

Then either:

- Terminated at spinal cord

- Travels up via sensory pathways to the different parts in the brain

Specialised receptor cells - What do they do

Respond to stimuli to initiate responses by the nervous system

- Detects internal/external changes to the body

- Sends signals via nervous system to coordinate responses to maintain homeostasis

- Respond quickly/automatically to maintain balance

Proprioceptors - Purpose

Proprioceptors help us to sense body position and movement

Proprioceptors - Function

- Detects changes in muscle length, joint angle and tension

- They provide information about body positioning (helps to maintain balance)

Proprioceptors - Location

Found in muscles, tendons, joints and inner ear

Proprioceptors - Goal

To help the body maintain coordination, balance, posture and movement accuracy by sensing the position and movement of muscles and joints.

Proprioceptors - Example of purpose

- Monitor head and limb location and movement

- Monitor tension on the tendons

- Monitor the position of joints

- Monitor the degree to which muscles are contracted

Proprioceptors - Example response

- Helps maintain balance and coordination during movement

- Allows for quick adjustments to posture and technique

Chemoreceptors - Purpose

Sense chemical changes in the blood

Chemoreceptors - Function

Detects levels of oxygen, carbon dioxide and blood pH

Chemoreceptors - Location

In major arteries (e.g. carotid bodies) and in the brainstem.

Chemoreceptors - Goal

Monitor the chemical composition of the blood to help maintain homeostasis

- Especially through adjustments in breathing rate and depth

Chemoreceptors - Example of purpose

Monitors changes in:

- Oxidation levels of blood (O2 blood)

- CO2 level or acidity of the blood

- The hydrogen ions which also aligns with lactic acid build up

Chemoreceptors - Example response

If CO2 levels increase or pH drops, chemoreceptors send signals to medulla oblongata to increase ventilation to expel more CO2 = maintain acid-base balance.

Baroreceptors - Purpose

Sense blood pressure changes and send signals to the brainstem.

Baroreceptors - Function

Detect changes in blood pressure (arterial pressure)

- Sends signals to the brain stem

Baroreceptors - Location

In the walls of major arteries

- E.g. aorta and carotid arteries

Baroreceptors - Goal

Maintain stable blood pressure and ensure adequate blood flow to the brain and muscles

Baroreceptors - Example of purpose

- Stretch sensitive sensory receptors located in walls of large arteries

- Monitors blood pressure by detecting stretch of arterial walls as blood flows

Baroreceptors - Example response

- If blood pressure drops, less stretch in artery walls is detected, reduction of rate of nerve impulses sent to brain; brain activates sympathetic nervous system and heart rate increases.

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