7. Nervous Control of Muscular Movement Flashcards
2 Divisions of the Nervous System
A. Central Nervous System (CNS) –
Brain and Spinal Cord
B. Peripheral Nervous System (PNS) - Afferent and Efferent divisions
3 parts of the brain
a) Forebrain
(i) Cerebrum constitutes about 80% of total brain weight
- cerebral cortex, basal nuclei
(ii) Diencephalon - thalamus, hypothalamus
b) Cerebellum
c) Brainstem - continuous with the spinal cord - medulla, pons, midbrain
Organization of the Nervous System
Afferent vs Efferent
Afferent is information going out
Efferent is information coming in
Cerebral Cortex of the Brain
Bones in the skull
What is the Spinal Cord?
transmitting sensory and motor information between the brain and the rest of the body.
- long cylinder of nerve tissue which extends down from the brainstem to the second lumbar vertebrae.
- 45 cm long and 2 cm in diameter.
- Protected by the vertebral column and associated ligaments and muscles,
- the spinal meninges
- the cerebrospinal fluid.
Meninges on Spinal Cord
Peripheral Nervous System consists of…
12 pairs of cranial nerves
31 pairs of spinal nerves
How many pairs of CRANIAL nerves do we have? Number and Name them. (name 3)
What is the Afferent Division?
- Afferent division
- conveys information from the sensors in the
periphery to the central nervous system (CNS)
What is the Efferent division?
a) Somatic nervous system -
nerve fibers innervate skeletal muscle
b) Autonomic nervous system
- nerve fibers innervate smooth and cardiac
muscle and glands
(i) sympathetic division
(ii) parasympathetic division
Sympathetic vs Parasympathetic
Sympathetic and Parasympathetic effects
(white out table)
The nervous system consists of what two categories of cells?
Neuroglia and Neurons
What is Neuroglia? (4)
- comprise about 90% of the cells within the CNS.
- occupy about half of the volume of the brain.
- The four major types of glial cells serve as the connective tissue of the CNS and as such help support the neurons both physically and metabolically.
- It is estimated that there are 100 billion neurons in the brain and one trillion neuroglia.
What are Neurons?
Neuron
* Excitable
* Carry electrical signals
Examples of the Neuroglia?
What are Neurons comprised of?
- a nerve cell.
- neuron is specialized to transmit electrical signals.
- Cell body
- Axon
- Dendrites
Basic Structure of a Neuron
What are the Cell body and Axon?
- Cell body - soma - contains the nucleus
- Axon - a long fiber that conducts impulses away from the cell body.
The term “nerve fiber” is generally used in reference to an axon.
Basic Structure of a Neuron
What is a Dendrite?
A dendrite is a branch-like extension on a neuron (nerve cell) that receives incoming signals from other neurons. It acts like a receiver, gathering information and transmitting it towards the cell body, where the neuron processes these signals to determine whether to generate its own electrical impulse (action potential) for communication with other neurons.
What is the Myelin Sheath? (2)
Myelin sheath
- It is composed mainly of lipid and protein.
- insulates axons and speeds up nerve impulse transmission by allowing action potentials to jump between nodes of Ranvier
What are the Nodes of Ranvier?
Nodes of Ranvier - spaces between the segments of myelin sheath
! saltatory conduction
Why do we have Myelinated nerve fibers?
- Myelinated nerve fibers have much faster conduction velocities than unmyelinated fibers
What is Multiple Sclerosis?
Autoimmune disease – body attacks myelin sheath within CNS
* Break down in communication
* Exposed nerves can be destroyed irreversibly
* Fatigue, vision changes, numbness, loss of coordination, muscle weakness, cognitive dysfunction
What is a Synapse?
What is a Chemical Synapse?
Synapse – the region where a neuron meets its target cell
– axon to dendrite
– axon to muscle cell
Chemical synapse –
electrical signal converted to chemical signal for transmission to the postsynaptic cell
Neurons are divided into what 3 functional classes?
- Afferent neurons - carry impulses from the sensory receptors into spinal cord or brain
- Efferent neurons - transmit impulses from the CNS out to the effector organs - muscles (motor neurons) and glands
- Interneurons - lie entirely within the CNS. They account for 99% of all nerve cells.
What is Resting membrane potential?
The resting membrane potential is the electrical charge difference that exists across the cell membrane of a neuron or other excitable cells when they are not actively transmitting signals. In other words, it’s the baseline electrical state of the cell when it’s not firing an action potential.
In most neurons, the inside of the cell is negatively charged compared to the outside. This charge difference is typically around -70 millivolts (mV) in neurons. This difference in charge is maintained by the movement of ions, such as sodium (Na+), potassium (K+), and chloride (Cl-), through ion channels in the cell membrane. Sodium-potassium pumps also play a role in maintaining this potential by actively transporting sodium ions out of the cell and potassium ions into the cell.
What is an Action potential?
An action potential, also known as a nerve impulse, is a brief electrical signal that travels along the membrane of a neuron. It’s a fundamental mechanism by which neurons communicate with each other and transmit information within the nervous system.
What is the Synaptic Cleft?
Nervous information is relayed across the synaptic cleft by means of a chemical transmitter substance.
Excitatory vs Inhibitory
What is the Neuromuscular Junction?
Neuromuscular junction - nerve to muscle synapse. The chemical transmitter substance is acetylcholine.
What are Schwann Cells?
Schwann cells secrete chemical signals required for formation and maintenance of the Neuromuscular Junction
What is ACH?
the chemical transmitter substance is acetylcholine (Ach)
What is the Spinal Cord?
- The spinal cord provide two-way conduction pathway to and from the brain, and it is a major reflex centre.
- Paired spinal nerves arise from the spinal cord
- 31 pairs of spinal nerves are attached to the spinal cord
What are the Cervical spinal nerves?
What is cervical enlargement?
The cervical enlargement which extends from the C4 through T1 segments of the spinal cord
What is The lumbosacral enlargement?
The lumbosacral enlargement which extends from the T11 through L1 segments of the spinal cord
What is the Plexus?
Plexus – a network of converging and diverging nerve fibers, or blood vessels
differentiate between grey and white matter?
The brain and spinal cord are composed of gray matter and white matter.
- The nerve cell bodies lie in and constitute the grey matter
*axons form the white matter.
Dorsal vs Ventral Roots
Each spinal nerve has a dorsal (back) root and a ventral (front) root connected to the spinal cord.
- The dorsal roots contain afferent (sensory) fibers that carry information from the periphery to the spinal cord and brain.
- The ventral roots contain efferent (motor) fibers to the skeletal muscle.
Where are the Dorsal and Ventral Roots?
Each spinal nerve has a dorsal root and a ventral root connected to the spinal cord.
The dorsal roots contain afferent (sensory) fibers that carry information from the periphery to the spinal cord and brain.
The ventral roots contain efferent (motor) fibers to the skeletal muscle.
The cell bodies of the motor axons making up the ventral roots are located in the ventral gray horns of the spinal cord
The cell bodies of the sensory axons making up the dorsal roots are outside of the spinal cord in the spinal ganglia
What are the Five functional components of the reflex arc? (ON EXAM)
Five functional components
* Receptor (muscle spindle)
* Afferent (sensory) neuron
* Integrating Centre (spinal cord)
* Efferent (motor) neuron (both alpha and gamma)
* Effector (muscle contraction)
What are Golgi Tendon Organs (GTO)?
In summary, Golgi tendon organs are sensory receptors that monitor muscle tension and contribute to maintaining safe levels of force during muscle contractions, helping to prevent injury and regulate muscle activity.
They are in series with the muscle fibers rather than in parallel as are muscle spindles.
- When a muscle contracts, the GTO is stretched.
What are The cerebral cortex and cerebellum?
The cerebral cortex and cerebellum are the main centers
employed in learning new motor skills. These areas of the brain
initiate voluntary control of movement patterns.
What is the Primary motor cortex?
located at the rear of the frontal lobe of the cerebral cortex.
- Stimulation of different areas of the primary motor cortex brings about movement in different, specific areas of the body.
- Contains the motor homunculus. However, no coordinated movement can be elicited.
Motor Homunculus
What is the Premotor Cortex?
One of the three higher areas that command the primary motor cortex.
- Located on the lateral surface of each cerebral hemisphere in front of the primary motor cortex.
What is the Somatosensory Cortex?
Somatosensory Cortex
- The site for initial cortical processing of pressure, touch, heat pain and proprioceptive input
- Located in the anterior section of the parietal lobe, immediately behind the central sulcus.
- Each region within the somatosensory cortex receives sensory input from a specific area of the body.
Where is the Cerebellum?
