Lec 1- Intro to the Nervous System

Question 1

PNS is composed of:

Answer 1

Nerve fibres and ganglia (collections of nerve cell bodies)

Question 3

What is Sensory / Afferent?

Answer 3

Component of the nervous system that conveys information from sensory organs and receptors in the Peripheral Nervous System (PNS) to the Central Nervous System (CNS) for processing and perception.

Question 4

What is Motor / Efferent?

Answer 4

Responsible for transmitting commands from the Central Nervous System (CNS), which includes the brain and spinal cord, to the Peripheral Nervous System (PNS) to initiate muscle contractions and other bodily responses.

Question 5

Is the boundary between sensory and motor ambiguous in the PNS and most of the spinal cord?

Answer 5

No, the boundary between sensory and motor functions is not ambiguous in the PNS and most of the spinal cord. In these areas, afferent (sensory) and efferent (motor) signals travel in opposite directions along distinct fibers, making their separation clear.

Question 6

Somatic System

Answer 6

Described as being associated with conscious and voluntary actions, however its not strictly true as many muscular actions are not conscious

Question 7

What is the target of all efferent output in the somatic system?

Answer 7

All efferent output in the somatic system goes to skeletal muscles.

Question 8

Autonomic system

Answer 8

Usually described as being unconscious and involuntary.

Question 9

Where does the efferent output of the autonomic system go?

Answer 9

The efferent output of the autonomic system goes to cardiac muscles, smooth muscles, and glands.

Question 10

What are the sub-components of the autonomic system?

Answer 10

The autonomic system is divided into three sub-components: sympathetic, parasympathetic, and enteric.

Question 11

Sympathetic Nervous System

Answer 11

Generally associated with rapid responses
“Fight or flight”
- Not all sympathetic functions are emotionally charged in this way

Question 12

Parasympathetic Nervous System

Answer 12

generally associated with slower responses and is often described as “rest and digest”?

Question 13

How do the parasympathetic and sympathetic nervous systems typically interact with the same structures in the body?

Answer 13

They often work in opposite ways, creating a push/pull relationship. For example, parasympathetic activity decreases heart rate and constricts pupils, while sympathetic activity does the opposite.

Question 14

Is the interaction between the parasympathetic and sympathetic systems antagonistic or complementary?

Answer 14

It is complementary rather than antagonistic, as both systems work together to maintain balance and regulation in the body.

Question 15

What is the general role of the parasympathetic and sympathetic systems in regulating each other?

Answer 15

In general, these systems provide negative feedback regulation to actively produce homeostasis in the body.

Question 16

Where is the enteric nervous system located?

Answer 16

The enteric nervous system is entirely housed within the digestive tract.

Question 17

Why do some argue that the enteric nervous system is not really part of the autonomic system?

Answer 17

Some argue that the enteric nervous system is not truly part of the autonomic system because it can function effectively even if surgically separated from the sympathetic and parasympathetic systems.

Question 18

What does “Rostral” mean in anatomical terms?

Answer 18

Rostral means forward or toward the front of an organism.

Question 19

What does rostral mean in the brain?

Answer 19

In the brain, it refers to structures closer to the front or anterior part of the brain

Question 20

What is the definition of “Caudal” in anatomy?

Answer 20

Caudal means backward or toward the tail of an organism.

Question 21

What does rostral mean in the spinal cord?

Answer 21

It describes structures closer to the head or cranial end.

Question 22

What does caudal mean in the brain?

Answer 22

.In the context of the brain, it refers to structures closer to the back or posterior part of the brain.

Question 23

What does caudal mean in the spine?

Answer 23

In the spinal cord, it is used to describe structures closer to the tail or caudal end.

Question 24

What does “Dorsal” mean in anatomical terms, and where is it used differently?

Answer 24

Dorsal means up or toward the back of an organism. In the brain, it refers to structures located toward the top or superior part of the brain. However, in the spinal cord, it describes structures located toward the back or posterior part of the spinal cord.

Question 25

What is the anatomical definition of “Ventral” and how does it vary in the brain and spinal cord?

Answer 25

Ventral means down or toward the belly of an organism. In the brain, it refers to structures located toward the bottom or inferior part of the brain. In the spinal cord, it describes structures located toward the front or anterior part of the spinal cord.

Question 26

What is the primary function of dendrites in a neuron?

Answer 26

Dendrites receive (most) incoming signals from other neurons.

Question 27

What is the role of axons in a neuron?

Answer 27

Axons send signals away from the soma (cell body) to transmit information to other neurons.

Question 28

What is found at the end of axons, where communication with other neurons occurs?

Answer 28

At the end of axons, there are synapses, where signals are transmitted to other neurons.

Question 29

What happens when neurotransmitter molecules are released from the axon?

Answer 29

Neurotransmitter molecules are released from the axon and bound to receptors on the dendrites (or soma) of other neurons, facilitating communication.

Question 30

What is the purpose of myelin sheathes in neurons?

Answer 30

Myelin sheathes increase the fidelity and speed of signal transmission along axons.

Question 31

What happens when there is no myelin sheath around an axon?

Answer 31

Without a myelin sheath, signals can disperse out of the axon, leading to less efficient transmission.

Question 32

What distinguishes principal or projection neurons?

Answer 32

Principal or projection neurons have long axons that extend beyond their immediate structure and terminate elsewhere, allowing for long-distance communication.

Question 33

What characterizes intrinsic or interneurons?

Answer 33

Intrinsic or interneurons have shorter axons, which are primarily used for local communication within a specific region of the nervous system.

Question 34

Why are areas with many grouped axons of projection neurons called “white matter” in living tissue?

Answer 34

White matter in living tissue appears white because it consists mainly of myelinated axons

Question 35

What characterizes areas with many somas in the nervous system, leading to them being called “grey matter”?

Answer 35

Grey matter in the nervous system is characterized by regions with many cell bodies (somas)

Question 36

How is the arrangement of white matter and grey matter typically seen in the spinal cord?

Answer 36

In the spinal cord, white matter (outside) surrounds grey matter.

Question 37

Is the arrangement of white matter and grey matter the same throughout the entire nervous system?

Answer 37

No, the arrangement varies. In the upper brain, the reverse is generally true, where grey matter surrounds white matter (outside).

Question 38

White matter is associated with:

Answer 38

long-distance information transmission.

Question 39

How does white matter appear in stained pictures compared to grey matter?

Answer 39

White matter typically appears darker than grey matter in stained pictures due to differences in staining properties.

Question 40

Grey matter is associated with:

Answer 40

local information processing

Question 40

What is the grey matter at the surface of the brain often referred to as?

Answer 40

The grey matter at the surface of the brain is called the cortex or neocortex.

Question 40

Why is it called the “neocortex”?

Answer 40

It is termed “neocortex” because it is evolutionarily younger than the rest of the brain, reflecting its more recent development in evolutionary history.

Question 40

How does the amount of cortex vary across different species?

Answer 40

There is much more cortex in mammals than in reptiles, more in primates than in other mammals, and even more in humans compared to other primates.

Question 41

How is brain surface area related to its level of wrinkliness?

Answer 41

Wrinkly brains tend to have more surface area due to the folding of the cortex.

Question 42

What are the inward wrinkles on the brain’s surface called, and what are the outward wrinkles called?

Answer 42

The inward wrinkles are called sulci or sulcus, and the outward wrinkles are called gyri or gyrus.

Question 43

What are the five main regions of the vertebral column?

Answer 43

The five main regions of the vertebral column are cervical (neck), thoracic (ribcage), lumbar (lower back), sacral, and coccygeal.

Question 44

What is the role of the spinal cord within the vertebral column?

Answer 44

It serves as the primary pathway for transmitting sensory and motor signals between the body and the brain.

Question 45

Horn (Dorsal/posterior, ventral/anterior, lateral)

Answer 45

Areas within spinal grey matter, typically seen in cross section

Question 46

Columns (Dorsal/posterior, ventral/anterior, lateral, ventrolateral/anterolateral)

Answer 46

long connections up and down spine, within spinal white matter

Question 47

Roots (Dorsal/posterior, ventral/anterior)

Answer 47

beginnings of the PNS and spinal nerves - outside the spine

Question 48

What type of connections are typically found in the dorsal or posterior horn of the spinal cord?

Answer 48

The dorsal or posterior horn of the spinal cord contains afferent connections, which are responsible for receiving incoming sensory information.

Question 49

What type of connections are located in the ventral or anterior horn of the spinal cord?

Answer 49

The ventral or anterior horn of the spinal cord contains somatic efferent connections, which transmit signals to skeletal muscles for motor control.

Question 50

What type of connections are present in the lateral horn of the spinal cord?

Answer 50

The lateral horn of the spinal cord contains sympathetic efferent connections, which control functions such as cardiac, smooth muscle, or glandular activity.

Question 51

Are there lateral horns in all regions of the spinal cord?

Answer 51

No, there are no lateral horns in the cervical or lower lumbar junctions of the spinal cord, meaning there are no sympathetic efferent connections in these regions.

Question 52

What are spinal nerves composed of?

Answer 52

Spinal nerves are bundles of neurons that contain both afferent (sensory) and efferent (motor) fibers.

Question 53

What are the main components of a spinal nerve?

Answer 53

A spinal nerve consists of ventral and dorsal roots, dorsal root ganglia (also known as spinal ganglia), and four rami (branches).

Question 54

Dorsal Ramus:

Answer 54

The dorsal ramus is a branch of a spinal nerve that carries sensory and motor signals to and from the muscles and skin of the back.

Question 55

Ventral Ramus

Answer 55

The ventral ramus is a branch of a spinal nerve responsible for carrying signals to and from the muscles and structures on the front and sides of the body.

Question 56

White Ramus

Answer 56

A short myelinated nerve fiber that connects the spinal nerve to the sympathetic ganglia in the autonomic nervous system.

Question 57

Grey Ramus

Answer 57

Unmyelinated nerve fiber that carries post-ganglionic sympathetic fibers back from the sympathetic ganglia to the spinal nerve.

Question 58

Where are the cell bodies of sensory neurons located?

Answer 58

Sensory neurons have cell bodies in the dorsal root ganglion, which is located outside the spine.

Question 59

Are there synapses in the dorsal root ganglia?

Answer 59

No, there are no synapses in the dorsal root ganglia

Question 60

What are the three types of axonal projections from dorsal root ganglia into the spine?

Answer 60

1)Rostrally to the brain (majority of connections).
T2) To an interneuron in the dorsal horn, which projects to a motoneuron in the ventral horn, which, in turn, projects to skeletal muscle (forming a three-neuron reflex arc).
3) Directly to a motoneuron in the ventral horn, which projects to skeletal muscle (forming a two-neuron reflex arc).

Question 61

How do somatic efferent projections leave the ventral horn?

Answer 61

Somatic efferent projections leave the ventral horn through the ventral root and eventually synapse directly on skeletal muscles.

Question 62

What is the path taken by sympathetic efferent projections as they leave the lateral horn?

Answer 62

Sympathetic efferent projections leave the lateral horn via the ventral or anterior root and curve down the white ramus.

Question 63

What are the initial sympathetic neurons that leave the CNS called?

Answer 63

The initial sympathetic neurons that leave the CNS are termed pre-ganglionic neurons. Their axons, known as pre-ganglionic fibers, are myelinated

Question 64

Where do pre-ganglionic sympathetic neurons usually connect with other neurons?

Answer 64

Pre-ganglionic sympathetic neurons usually connect with post-ganglionic neurons in groups of nerve cell clusters called sympathetic ganglia, which can be found either close to the spine or a bit farther away in collateral ganglia.

Question 65

What type of axons do post-ganglionic sympathetic neurons have, and what do they project to?

Answer 65

Post-ganglionic sympathetic neurons have unmyelinated axons (post-ganglionic fibers) that project to smooth muscles, cardiac muscles, and glands, either through the gray ramus that rejoins the spinal nerve or through independent connections

Question 66

Efferent spinal connections involve two main types of innervation:

Answer 66

1) Autonomic Innervation: Controls involuntary functions such as heart rate, digestion, and glandular activity.
2) Somatic Motor Innervation: Efferent pathways that control voluntary muscle movements.