Tissues and Functions of the Nervous System

What are the two main divisions of the nervous system?

The central nervous system (CNS) and the peripheral nervous system (PNS).

What is the primary function of the somatic nervous system?

To interact with the external environment.

What is the primary function of the autonomic nervous system?

To maintain a functional internal environment, such as regulating heart rate, respiration, and circulation.

What does the principle of 'constant activity & system behavior' in the nervous system refer to?

There is constant sensory input to the nervous system, but it can respond selectively.

What does 'multiple centers for control' mean in the context of nervous system organization?

Information is processed in several areas of the CNS, with decisions made at various levels.

What is the significance of the hierarchy principle in the nervous system?

The cortex is responsible for all decisions, but immediate reflex actions can occur in the spinal cord and brainstem without conscious awareness.

How does feedback function in the nervous system?

The CNS learns from experiences and evaluates the results of actions, which can lead to changes in PNS detection.

What is serial processing in the nervous system?

A linear connection, such as the reflex arc.

What is parallel processing in the nervous system?

Various areas of the CNS process information simultaneously.

What are emergent properties in the context of the nervous system?

The ability of multiple centers of the CNS to process information, resulting in a richer experience than if processed separately.

What does adaptation refer to in neuronal function?

Neuronal plasticity, where connections between neurons are modifiable and adaptable, allowing for learning and pruning of ineffective strategies.

Why are theories of CNS organization important for occupational therapists?

They help understand motor functions and how clients can engage in occupations.

What is the role of theories in understanding the CNS and PNS?

They explain functions and help understand what happens when things do not work correctly.

What is an example of a functional principle of nervous system organization?

Feedback, where the CNS learns from experiences.

What does the term 'neuronal plasticity' refer to?

The ability of neurons to form new connections and adapt, facilitating learning.

What is the significance of the phrase 'engage the brain before the mouth'?

It illustrates the top-down model of decision-making in the cortex, relevant for speech production.

What happens in the spinal cord during a reflex action?

The decision to lift a foot after stepping on something sharp occurs without conscious awareness.

What is the importance of learning to read Braille in relation to the nervous system?

It demonstrates how the CNS can learn to detect differences in patterns through feedback.

What does the term 'pruning' refer to in neuronal adaptation?

The process by which the CNS eliminates ineffective neural connections.

What is the relationship between sensory input and nervous system response?

The nervous system receives constant sensory input but can selectively respond based on the situation.

What is the overall goal of understanding the theories of CNS organization?

To appreciate the complexity of the PNS and CNS and their functions.

What is the main focus of Reflexive Theory?

It provides a specific stimulus to produce a specific response, developed by Sherrington.

Who developed the Hierarchical Theory of motor control?

Hughlings Jackson in the late 1800s/early 1900s.

What does the Systems Theory emphasize in movement?

It explains movement as the synergistic action of several muscles working together.

What are central pattern generators (CPG) and where are they located?

CPGs are neural networks in the spinal cord and brainstem that produce rhythmic motor patterns, such as walking and swallowing.

What is a limitation of Reflexive Theory?

It does not explain intention or how responses are modified by the environment.

How does the Hierarchical Theory explain motor behavior control?

It suggests that higher cortical levels control lower centers in the CNS, allowing for initiated actions.

What is a practical example of the Hierarchical Theory in action?

The process of generating speech, where thoughts occur before speech is produced.

What did Bernstein contribute to the understanding of motor control?

He developed Systems Theory, viewing human movement from a mechanical perspective.

What is a limitation of Systems Theory?

It does not address how the environment influences motor control or issues of motivation.

What is the significance of the term 'synergy' in Systems Theory?

It refers to the coordinated action of various muscles to achieve smooth and efficient movement.

What does the Reflexive Theory suggest about complex movements like walking?

It indicates that complex movements can occur without overt cognitive monitoring due to CPGs.

What does the Hierarchical Theory fail to account for in terms of reflex actions?

It does not address the automatic and reflexive aspects of actions, such as quickly lifting a foot from a sharp object.

How does the Systems Theory view the body during movement?

It views the body as a linked system where multiple joints and muscles work together for efficient movement.

What is an example of a limitation of the Reflexive Theory related to brain injury?

Individuals with traumatic brain injuries may have compromised abilities to perform automatic actions like swallowing.

What does the term 'top-down model' refer to in the context of Hierarchical Theory?

It refers to the idea that higher brain centers control lower centers in the nervous system.

What is the relationship between intention and movement according to the theories discussed?

Reflexive Theory does not explain intention, while Hierarchical Theory suggests intention is initiated by higher brain functions.

What is a common example used to illustrate the action of CPGs in the Reflexive Theory?

Walking, where the spinal cord coordinates movement without conscious thought.

How does motivation influence movement according to Systems Theory?

It affects the control and quality of movements displayed in different contexts, such as rehearsals versus performances.

What does the term 'mechanical perspective' imply in Systems Theory?

It implies that human movement is viewed in terms of physical laws and the body's mechanical linkages.

What is the role of the environment in motor control as per the discussed theories?

While Systems Theory acknowledges the body's mechanics, it does not fully address environmental influences on motor control.

What is a key takeaway regarding the limitations of the theories discussed?

Each theory has its strengths but also significant limitations in explaining all aspects of motor control.

What does Dynamical Action theory explain about movement?

It explains movement as the synergistic action coupled with the velocity of movement, where coordination changes with changes in velocity.

Who were the originators of Dynamical Action theory?

Thelan, Kelso & Tuller, and Perry.

How does Dynamical Action theory relate to Bernstein's work?

It builds upon Bernstein's work with an emphasis on the energy consumption of motor action.

Provide an example of Dynamical Action theory in practice.

Quickly walking to catch a bus, where the change from walking to running reflects an efficiency issue.

What is a common example used to illustrate changes in gait patterns in Dynamical Action theory?

Observing a horse move through various gait patterns from walking to trotting.

What is a limitation of Dynamical Action theory?

It does not consider the importance of the CNS/PNS, viewing them as subservient to the mechanical coupling of joints and muscles.

What does the Task Oriented approach emphasize in relation to movement?

It emphasizes how the environment and task demands influence movement strategies.

Who contributed to the development of the Task Oriented approach?

Bass-Haugen & Mathiowetz, and Horak.

How do neurons function in the Task Oriented approach when learning a new task?

Initially, many neurons fire to process multiple pieces of information, but this pool shrinks as the task is learned.

Give an example of how a child learns to walk in the context of the Task Oriented approach.

A child experiences stress and demands as neurons fire to assess the constraints of the task, such as how to hold an object.

What is a limitation of the Task Oriented approach?

There is no consistent means to determine which features should be highlighted for learning a specific task, as this may vary by individual.

What does the Ecological approach focus on regarding movement?

It focuses on environmental features and perceptions, particularly how we detect pertinent information in our environment.

How does the Ecological approach impact motor behavior?

It examines how the information from the environment influences motor behavior.

What is emphasized in the perception of the environment when performing motor tasks?

The personal perception of the environment is considered more crucial than the sensory experience.

Who developed the theory emphasizing personal perception in motor tasks?

James J. Gibson, a psychologist interested in human-environment interaction.

What is a limitation of Gibson's theory on perception?

It places less emphasis on the specific functions of the central nervous system (CNS) and focuses more on a global model of perception.

What is the role of connective tissue in the PNS and CNS?

To support and protect the structures it surrounds.

What are the three layers of connective tissue in the PNS?

Epineurium (outer layer), perineurium (middle layer), and endoneurium (innermost layer).

What does the epineurium surround?

The entire nerve by collecting individual bundles of fibers.

What is the function of the perineurium?

It surrounds each bundle of nerve fibers.

What protective structures support the CNS?

The meninges (dura mater, arachnoid mater, pia mater) and the skull and vertebral column.

What is the role of the cell body (soma) in a neuron?

It contains cytoplasm and the nucleus, serving as the 'metabolic engine room' to keep the cell alive.

What happens to the axon when it is severed in a peripheral nerve injury?

The distal portion degenerates, while the proximal portion connected to the cell body is preserved.

At what rate does axon regeneration occur in the PNS?

Approximately one inch per month.

Does axon regeneration guarantee total recovery of function?

No, regeneration does not ensure total recovery, and the axon may not connect to the correct structures.

Where are the sensory cell bodies located in the PNS?

In the dorsal root ganglion.

Where are the motor cell bodies located in the PNS?

In the anterior horn of the spinal cord.

What is necessary for the conductance of an impulse in the PNS?

The integrity of the axon and the presence of myelin, which is an insulating fiber.

What type of cells form myelin in the PNS?

Schwann cells.

Who discovered Schwann cells?

Theodor Schwann.

What is the significance of the dorsal root ganglion in the PNS?

It contains the cell bodies of sensory neurons.

What is the significance of the anterior horn in the spinal cord?

It contains the cell bodies of motor neurons.

What is the relationship between the axon and the cell body?

The axon is dependent on the cell body for survival.

What types of fibers do peripheral nerves contain?

Fibers from both sensory neurons and motor neurons.

What is the function of the myelin sheath around the axon?

It forms a tube around the axon and allows the impulse to be propagated along the axon to the axon terminal.

What happens if the myelin sheath is preserved when the axon is severed?

It provides a guide for the re-growth (regeneration) of the axon, which occurs at a rate of about one inch per month.

What are the two types of fibers in the PNS?

Myelinated fibers, where each axon has its own myelin sheath, and unmyelinated fibers, where axons share a myelin sheath.

What is the Node of Ranvier?

The breaks between the wrapped sheath of myelin along the axon.

What role do Schwann cells play in the PNS?

They can regenerate the myelin sheath if the cell body has not been damaged.

What happens if the Schwann cell's cell body (soma) is destroyed?

The Schwann cell cannot regenerate the myelin sheath.

How many Schwann cells can wrap around a single myelinated axon?

Several Schwann cells can wrap around a single myelinated axon.

What is the significance of the Schwann cell tunnel?

It is important for the regeneration of severed axons to reach the correct muscle or sensory organ.

What do afferent fibers do in the PNS?

They transmit sensory information into the spinal cord.

What do efferent fibers do in the PNS?

They transmit impulses to the muscles to activate them.

Describe the structure of the motor portion of the PNS.

The cell body is within the CNS, with dendrites close to the cell body, and the axon extends from the anterior horn of the spinal cord.

Describe the structure of the sensory portion of the PNS.

The cell body is in the periphery, with dendrites connecting to sensory organs and the axon projecting into the spinal cord.

What is the role of interneurons in the PNS?

They connect incoming sensory fibers to outgoing motor fibers.

What are the types of glial cells found in the CNS?

Astrocytes, oligodendrocytes, ependymal cells, radial cells, and microglia.

What is the primary function of astrocytes in the CNS?

They anchor neurons to their blood supply and regulate the external chemical environment of neurons.

How do astrocytes contribute to the blood-brain barrier?

They are thought to be the predominant building blocks of the blood-brain barrier.

What do astrocytes recycle during synaptic transmission?

They recycle neurotransmitters released during synaptic transmission.

What is the significance of the sensory receptor connected to an afferent nerve fiber?

It transmits information into the spinal cord regarding stimuli, such as a mosquito landing on the skin.

What is the relationship between the cell body of motor neurons and their axons?

The cell body is located in the CNS, while the axon extends into the peripheral nerves.

What is the regeneration rate of axons in the PNS?

Regrowth occurs at a rate of approximately one inch per month.

What distinguishes myelinated axons from unmyelinated axons in the PNS?

Myelinated axons have their own myelin sheath, while unmyelinated axons share a sheath with adjacent axons.

What role do astrocytes play in the blood-brain barrier?

Astrocytes are considered the predominant building blocks of the blood-brain barrier, regulating vasoconstriction and vasodilation.

How do astrocytes communicate with each other?

Astrocytes signal each other using calcium, facilitated by gap junctions that allow the messenger molecule IP3 to diffuse between them.

What is the effect of IP3 on astrocytes?

IP3 activates calcium channels on cellular organelles, releasing calcium into the cytoplasm, which may stimulate the production of more IP3, leading to a calcium wave.