Nervous System (6) Flashcards
The NERVOUS SYSTEM (2)
- The nervous system is the body’s way of gathering information, storing it, and responding to it.
- Main role is to assemble information about conditions EXTERNAL and INTERNAL to the body.
→ Analyze this information
→ Initiate responses that may be necessary to satisfy certain needs.
The BRAIN (3)
- Control center or “computer” of the body.
- Incapable of performing physical tasks therefore it sends commands to other parts of the body to perform them.
- 6 main parts: Cerebrum, cerebellum, brain stem, diencephalon, limbic system, and the reticular activation system.
Properties of the CEREBRUM (3)
- Largest part of the brain
- Contains nerve centers that control sensory and motor activities.
- Can be divided into two halves or “hemispheres”
→ Each hemisphere is divided into 4 lobes named after the bone they lie over.
→ Frontal lobe, temporal lobe, parietal lobe, occipital lobe.
Properties of the CEREBELLUM (3)
- Second largest region.
- Lies behind and below the cerebrum.
- Main function is to coordinate muscle movement and control balance.
Properties of the BRAIN STEM (3)
- Below cerebrum and in front of the cerebellum.
- Links the cerebrum with the spinal cord.
- Houses brain centers responsible for automatic functions, postural control, muscle tone, and eye movement.
Properties of the DIENCEPHALON (3)
- Consists of the thalamus and hypothalamus.
- THALAMUS: Relays most sensory stimuli to the cerebral cortex.
- HYPOTHALAMUS: Controls body temperature, appetite, emotions and various automatic functions.
Properties of the LIMBIC SYSTEM (1)
- Composed of a collection of structures that regulate basic drives.
→ i.e Hunger, aggression, emotional drives.
Properties of the RETICULAR ACTIVATING SYSTEM (4)
- Network of neurons.
- Fans out through the cerebral cortex.
- Directs information to appropriate centers for interpretation.
- Crucial for maintaining consciousness.
What is the PERIPHERAL NERVOUS SYSTEM? (3)
- Carries information in and out of the CNS using 2 different kinds of nerves:
- MOTOR NERVES - aka efferent (outwards) nerves carry information from the CNS to the body’s organs.
- SENSORY NERVES - aka afferent (inwards) nerves carry information from sensory receptors to the CNS.
Explain the AUTOMATIC NERVOUS SYSTEM (3)
- Subsystem of the PNS
- Controls involuntary actions (i.e heartbeat)
- Comprised of two branches that act as opposing systems:
→ SYMPATHETIC SYSTEM
→ PARASYMPATHETIC SYSTEM
Explain the SYMPATHETIC SYSTEM (2)
- Causes localized bodily adjustments to occur (i.e sweating)
- Prepares the body for emergencies
→ Involves release of adrenaline, increase heart rate, widening blood vessels and “fight for flight” response.
Explain the PARASYMPATHETIC SYSTEM (1)
- Helps the body return to normal after it has been altered by the sympathetic system.
→ Sympathetic system will increase heart rate, parasympathetic system will decrease heart rate to bring it back to its resting state.
Explain the SOMATIC NERVOUS SYSTEM (4)
- Responsible for our awareness of the external environment.
- Through this system, the PNS receives and processes information from receptors in the skin, voluntary, muscles, tendons and joints.
- Gives sensation of touch, pain, heat, cold balance, body position and muscle action.
- Handles the muscles in our extremities which allows us to move.
Introduction to the REFLEX ARC (3)
- Reflexes are an automatic and rapid response to a particular situation.
- If the command center for the reflex is located in the brain, it is called CEREBRAL REFLEX.
- If the command center of the reflex is located in the spinal cord, it is called SPINAL REFLEX.
What are AUTONOMIC REFLEXES? (3)
- Controlled by the autonomic division of the nervous system.
- Involve activation of smooth and cardiac muscles (involuntary muscles).
- Regulates bodily functions such as digestion, elimination, blood pressure, salivation and sweating.
What are SOMATIC REFLEXES? (1)
- Involve stimulation of skeletal muscles
voluntary muscles
Explain the REFLEX ARC (1) (5 steps)
The name given to the pathways along which the initial stimulus and corresponding response (message)
- RECEPTOR: Receives the initial stimulus i.e load noise.
- SENSORY NERVE (afferent nerve): carries the impulse to the spinal cord or brain.
- INTERMEDIATE NERVE FIBRE: Interprets the signal and issues an appropriate response.
- MOTOR NERVE (efferent nerve): carries the response message from the spinal cord to the muscle or organ.
- EFFECTOR ORGAN: Carries out the response i.e skeletal muscle moves hand away from danger.
What are PROPRIOCEPTORS? (3)
- Specialized receptors found in tendons, muscles and joints.
- Provides sensory information about the state of muscle contraction, the position of limbs and body posture and balance.
- This feedback is provided primarily by afferent (sensory) input from two sensory receptors:
→ Golgi tendon organs (GTO)
→ Muscle spindles
What are GOLGI TENDON ORGANS (5)
- Sensory receptors that terminate where tendons join the muscle fibers.
- Since they are aligned with the muscle, any stretching of the muscle also stretches the GTO.
- The job of GTO is to detect increased tension exerted in the tendon.
- When a change in tension is detected, an impulse is sent along AFFERENT (sensory) neurons to the CNS.
- The EFFERENT (motor) neurons transmit an impulse causing the muscle to relax, thus preventing injury.
What are MUSCLE SPINDLES (3)
- Lies parallel to the muscle fiber.
- Send constant signals to the spinal cord.
- Helps maintain muscle tension and tone (standing posture)
→ Unlike GTO, they are sensitive to change in length, not tension.
Explain the STRETCH REFLEX (2)
- Simplest spinal reflex.
2. Depends only on the single connection between primary afferent fibers (sensory) and motor neurons of the same muscle.
STEPS to the stretch reflex (5)
- The receptor (patellar ligament/ quadriceps groups) senses the act of the hammer against the patellar ligament through the MUSCLE SPINDLE (due to change in length).
- Message is transmitted along the afferent (sensory) nerve axon to the spinal cord.
- The afferent nerve synapses with the efferent pathway (motor nerve) at the intermediate nerve fiber.
- An impulse is transmitted along the efferent pathways (motor neurons) to the muscle.
- The motor units of the quadriceps contract to accommodate additional stretch and prevent injury.
What is RECIPROCAL INHIBITION? (2)
- During a reflex, the opposing muscle group is simultaneously stimulated.
- In a knee-jerk reflex the quadriceps contract to extend the knee while the hamstrings are inhibited in a slightly delayed response (they do not flex)
What are POLYSYNAPTIC REFLEXES? (2)
- With other spinal reflexes, one or more interneurons lie between the primary sensory fibers and the motor neurons.
- the more interactions involved, the more complex and slow the reflex.
What is the WITHDRAWAL REFLEX? (3)
- The withdrawal of a body part from a painful stimulus (body is in danger).
- Reflex action involves transferring the impulse from a sensory neuron to a motor neuron through a connecting interneuron in the spinal cord.
- Extremely rapid, the brain doesn’t have time to interpret information.
What is REFLEX TESTING? (3)
- Important medical diagnostic tool.
- Weakm exaggerated or absent reflex response may indicate problems with portions of the nervous system.
- Can help determine the exact area of spinal injury.
Explain SPINAL CORD INJURIES (3)
- When the spinal cord receives a severe impact damage to the spine, it can affect its ability to send impulses to body parts.
- When there is a serious injury to the spinal cord, the nerves about the injury keep working.
- The nerves below the injury may or may not still function.
What is PARAPLEGIA? (1)
- The injury prevents the use of the legs but NOT the arms (injury on the spinal cord, after the neck).
What is QUADRAPLEGIA? (1)
- The injury prevents movement in both the arms and legs (injury at the beginning of the spinal cord).
What is the REHABILITATION process (3)
- Involves extensive physiotherapy (maybe surgery).
- Counselling to help the person and their family deal with the new situation.
- May be able to regain mobility in damaged limbs (after swelling has gone down).
Head injuries - CONCUSSIONS (3)
- Much more common than spinal cord injuries.
- CONCUSSIONS result from a blow to the head, literally shaking the brain within the skull.
→ Often involves injury to the nerve fibers.
→ Can be mild or severe.
→ Brain cells become abnormal and do not function properly. - Second direct or indirect impact can cause dangerous changes in the brain’s blood supply.
→ Leads to rapid swelling leading to coma or death.
Vertebral Column and the Spinal Cord (4)
- Main pathway for information connecting the brain and peripheral nervous system.
- Spinal cord runs through the vertebrae.
→ Starts from the base of the brain stem and travels down to the second lumbar vertebra.
→ Spinal nerves carry sensory information towards the CNS and motor commands away from the CNS.