Compendium 9

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Questions and Answers

What is the function of the spinal cord's enlargements in the cervical and lumbar-sacral regions?

They correspond with the limbs, with the cervical enlargement supplying the arms and the lumbar-sacral supplying the legs.

Name the three layers of meninges that protect the spinal cord.

Dura mater, arachnoid mater, and pia mater.

What is the role of the medulla oblongata in the brainstem?

It maintains homeostasis by regulating autonomic functions such as heart rate and breathing.

How many pairs of spinal nerves are there, and what does this tell us about the relationship between spinal nerves and vertebral bones?

There are 31 pairs of spinal nerves, even though there are 30 vertebral bones; this is due to the emergence of C1 above the first vertebra. Signup and view all the answers

What is the primary sensory function of the dorsal roots of the spinal cord?

To carry sensory nerve signals into the spinal cord. Signup and view all the answers

Describe the composition of the brain in terms of neurons and neuroglial cells.

The brain comprises approximately 100 billion neurons and a trillion neuroglial cells. Signup and view all the answers

What is the main function of the cerebellum?

To coordinate locomotion and balance in association with the cerebrum. Signup and view all the answers

Explain the role of the pons in the brainstem.

The pons acts as a bridge between different parts of the brain and contains centers that regulate sleep and respiration. Signup and view all the answers

What are the three layers of connective tissue surrounding nerves?

Endoneurium, perineurium, and epineurium. Signup and view all the answers

How does the medulla oblongata contribute to the autonomic functions of the body?

It acts as an autonomic reflex center that regulates respiration, circulation, and other reflexes. Signup and view all the answers

What role does the hypothalamus play in the body's homeostasis?

It works with the endocrine system to regulate homeostasis. Signup and view all the answers

What sensory information does the midbrain process?

It processes auditory, visual, and tactile sensory information. Signup and view all the answers

Why doesn't the central nervous system require additional protective layers?

It already has protective layers, such as bone and meninges. Signup and view all the answers

What role does the thalamus play in sensory perception?

The thalamus acts as a sensory relay center, processing information from all senses except for smell. Signup and view all the answers

Describe two functions of the hypothalamus.

The hypothalamus regulates body temperature and maintains homeostasis through the endocrine system. Signup and view all the answers

What distinguishes the precentral gyrus from the postcentral gyrus?

The precentral gyrus is the primary somatic motor cortex that controls voluntary movements, while the postcentral gyrus is the primary somatic sensory cortex that processes sensory information. Signup and view all the answers

Identify one structural feature of the cerebrum and its significance.

Gyri are the elevated folds of tissue in the cerebrum, increasing the brain's surface area for processing. Signup and view all the answers

How does the epithalamus contribute to brain function?

The epithalamus, which includes the habenula and pineal gland, is involved in regulating emotional responses and circadian rhythms. Signup and view all the answers

What is the primary function of the cerebellum in motor control?

The cerebellum regulates fine motor control, balance, and posture during activities such as writing or playing an instrument. Signup and view all the answers

Explain the role of the limbic system related to the thalamus.

The limbic system, which includes the thalamus, regulates emotions, memories, and strong feelings. Signup and view all the answers

What is the significance of the longitudinal fissure in the cerebrum?

The longitudinal fissure separates the left and right hemispheres of the cerebrum. Signup and view all the answers

Which lobe of the brain is responsible for processing visual information?

The occipital lobe is responsible for processing visual information. Signup and view all the answers

What is the central sulcus and what does it separate?

The central sulcus is a groove that separates the frontal lobe from the parietal lobe. Signup and view all the answers

What is the function of the corpus callosum in the brain?

The corpus callosum connects the two cerebral hemispheres, ensuring the brain works as a unified system. Signup and view all the answers

Describe the role of the limbic system in emotional response.

The limbic system, known as the emotional brain, expresses emotions through gestures and can trigger emotional responses linked to memories. Signup and view all the answers

What composes the dura mater, and what are its two layers?

The dura mater is composed of fibrous connective tissue, and its two layers are the periosteal dura and meningeal dura. Signup and view all the answers

What is the function of the dural venous sinus?

The dural venous sinus collects venous blood that nourishes the brain and returns it to the heart. Signup and view all the answers

How does damage to the limbic system affect an individual?

Damage to the limbic system can cause memory impairment and affect emotional responses. Signup and view all the answers

What distinguishes the arachnoid mater from the dura mater in terms of structure?

The arachnoid mater is thin and flimsy, resembling cobwebs, unlike the thicker, fibrous dura mater. Signup and view all the answers

Explain the significance of the subdural space.

The subdural space contains serous fluid, which provides cushioning for the brain. Signup and view all the answers

What are dural folds and their purpose in the brain?

Dural folds are connective tissue partitions that extend deep into the brain, helping to hold it in place and prevent excessive movement. Signup and view all the answers

In what parts of the brain do the periosteal and meningeal dura fuse?

In some areas of the brain, the periosteal and meningeal dura layers fuse, meaning the dural venous sinus may not exist there. Signup and view all the answers

How does the composition of the limbic system relate to its function?

The limbic system's composition, which runs through the cerebral hemispheres and diencephalon, is linked to its functions in memory and emotions. Signup and view all the answers

What is the primary function of cerebrospinal fluid?

To protect the brain and spinal cord from trauma and provide buoyancy. Signup and view all the answers

How does the structure of the autonomic nervous system differ from the somatic nervous system?

The autonomic nervous system consists of two neurons in series, while the somatic nervous system uses one motor neuron. Signup and view all the answers

What are the two divisions of the autonomic nervous system and their primary functions?

The sympathetic division prepares the body for 'fight or flight', whereas the parasympathetic division promotes 'rest and digest'. Signup and view all the answers

Name the four brain ventricles and their arrangement.

The lateral ventricles, third ventricle, fourth ventricle, and they are continuous with each other. Signup and view all the answers

What is unique about the pia mater in regard to its relationship with the brain?

The pia mater is the deepest meningeal layer and sits tightly over the brain, making it non-removable. Signup and view all the answers

Describe the role of ependymal cells in the brain's ventricles.

Ependymal cells line the ventricles and help circulate cerebrospinal fluid using their cilia. Signup and view all the answers

What triggers the sympathetic nervous system responses, and what are some effects?

It is triggered during threatening situations, causing effects like increased heart rate and deeper breathing. Signup and view all the answers

What distinguishes cranial nerves from spinal nerves?

Cranial nerves emerge directly from the brain, while spinal nerves arise from the spinal cord. Signup and view all the answers

How does the composition of cerebrospinal fluid compare to blood plasma?

Cerebrospinal fluid has a similar composition but contains fewer proteins and has a different ionic concentration. Signup and view all the answers

What is the role of the hypothalamus in regulating the autonomic nervous system?

The hypothalamus integrates incoming information and communicates with other brain parts to execute responses. Signup and view all the answers

What part of the brain is significantly involved in the coordination of fine motor movements?

The cerebellum is primarily responsible for the coordination of fine motor movements. Signup and view all the answers

How does the structure of grey and white matter differ between the spinal cord and the brain?

In the spinal cord, white matter is on the outside and grey matter is on the inside, while in the brain, grey matter is on the outside and white matter is on the inside. Signup and view all the answers

In regard to memory, what distinction is made between short-term and long-term memory processing locations in the brain?

Short-term memory is mainly stored in the temporal lobe, whereas long-term memory is distributed across various regions of the brain. Signup and view all the answers

What are the key functions associated with the frontal lobe as impacted by damage, based on the case study of Phineas Gage?

Key functions of the frontal lobe affected include voluntary motor function, motivation, planning, aggression, and emotional regulation. Signup and view all the answers

What is the role of the vermis in brain function?

The vermis connects the two hemispheres of the cerebellum and plays a role in coordinating motor activity. Signup and view all the answers

What is the conus medullaris and where is it located in the spinal cord?

The conus medullaris is the pointed end of the spinal cord, typically located at the level of the first or second lumbar vertebra. Signup and view all the answers

What role does the arachnoid mater play in relation to the cerebrospinal fluid?

The arachnoid mater contains the subarachnoid space, which is filled with cerebrospinal fluid and serves to cushion and protect the brain and spinal cord. Signup and view all the answers

How are the spinal nerves organized in relation to the vertebral bones?

There are 31 pairs of spinal nerves that emerge from the spinal cord, but there are only 30 vertebral bones due to the cervical nerves C1-C8 exiting above the corresponding vertebrae. Signup and view all the answers

What distinguishes the grey matter from the white matter in the spinal cord?

Grey matter contains cell bodies of neurons and is found in the inner regions of the spinal cord, while white matter contains myelinated axons and is located in the outer regions. Signup and view all the answers

Describe the arrangement of the layers of connective tissue that surround a nerve.

Nerves are surrounded by layers of connective tissue: endoneurium surrounds individual axons, perineurium surrounds groups of axons (fascicles), and epineurium surrounds the entire nerve. Signup and view all the answers

What is the primary function of the pons in the brainstem?

The pons primarily acts as a bridge connecting different parts of the brain, facilitating communication between the cerebrum and cerebellum, and regulating respiration. Signup and view all the answers

Explain how the function of the medulla oblongata relates to homeostasis.

The medulla oblongata regulates autonomic functions essential for homeostasis, such as heart rate and breathing, maintaining vital processes without conscious thought. Signup and view all the answers

What is the significance of the cauda equina in relation to the spinal cord?

The cauda equina is a bundle of spinal nerve roots that emerges from the conus medullaris, allowing for the continuation of nerve signals beyond the spinal cord. Signup and view all the answers

What structure connects the two cerebral hemispheres and ensures the brain operates as a whole?

The corpus callosum connects the two cerebral hemispheres. Signup and view all the answers

How does the limbic system contribute to emotions and memory?

The limbic system plays a crucial role in processing emotions and is involved in memory formation. Signup and view all the answers

What is the function of the dural venous sinus within the meninges?

The dural venous sinus collects venous blood that nourished the brain and returns it to the heart. Signup and view all the answers

In what way can a particular smell trigger an emotional response?

Smells can evoke memories and emotions due to the limbic system's role in processing sensory information. Signup and view all the answers

Describe the role of dural folds in the brain.

Dural folds are connective tissue partitions that help stabilize the brain and prevent excessive movement. Signup and view all the answers

What are the two layers of the dura mater, and where are they located?

The dura mater consists of the periosteal dura, which attaches to the skull, and the meningeal dura, which is continuous with the spinal dura. Signup and view all the answers

Where does the limbic system run within the brain?

The limbic system runs through the medial aspect of the cerebral hemispheres and the diencephalon. Signup and view all the answers

What is a significant consequence of damage to the limbic system?

Damage to the limbic system can lead to memory impairment. Signup and view all the answers

Why is the arachnoid mater described as cobweb-like?

The arachnoid mater is described as cobweb-like because it is a thin, flimsy membrane that resembles fine webbing. Signup and view all the answers

What role does the corpus callosum serve in brain function?

The corpus callosum facilitates communication between the two hemispheres of the brain. Signup and view all the answers

What is the main function of the thalamus in the diencephalon?

The thalamus acts as the sensory relay center, processing information from all senses except smell. Signup and view all the answers

Which brain structure is responsible for maintaining homeostasis?

The hypothalamus is responsible for maintaining homeostasis through the endocrine system. Signup and view all the answers

What distinguishes the precentral gyrus from the postcentral gyrus?

The precentral gyrus is the primary somatic motor cortex, while the postcentral gyrus is the primary somatosensory cortex. Signup and view all the answers

Describe the significance of gyri and sulci in the cerebrum.

Gyri are elevated folds of brain tissue that increase surface area, while sulci are grooves that separate these folds. Signup and view all the answers

Which structures make up the epithalamus?

The epithalamus consists of the habenula and the pineal gland. Signup and view all the answers

What are the primary functions of the cerebrum?

The cerebrum is responsible for higher brain functions, including thought, memory, and voluntary movement. Signup and view all the answers

How does the diencephalon contribute to emotional regulation?

The diencephalon, especially the thalamus and hypothalamus, regulates mood and strong emotions like fear and rage. Signup and view all the answers

What role do the fissures within the cerebrum play?

Fissures, such as the longitudinal fissure, divide the cerebrum into hemispheres, enhancing functional specialization. Signup and view all the answers

Which lobe of the brain is primarily responsible for processing auditory information?

The temporal lobe is primarily responsible for processing auditory information. Signup and view all the answers

How do the functions of the cerebellum differ from those of the cerebrum?

The cerebellum coordinates voluntary movements and balance, while the cerebrum is involved in higher cognitive processes. Signup and view all the answers

What is the primary role of cerebrospinal fluid in the brain?

Cerebrospinal fluid protects the brain and spinal cord from trauma and provides buoyancy, reducing pressure on underlying structures. Signup and view all the answers

How are the sympathetic and parasympathetic divisions of the autonomic nervous system distinguished in terms of their functions?

The sympathetic division is associated with 'fight or flight' responses, increasing heart rate, while the parasympathetic division promotes 'rest and digest', lowering heart rate and enhancing digestion. Signup and view all the answers

Identify the types of cells found in the choroid plexus and their significance.

The choroid plexus is composed of specialized ependymal cells, support tissue, and blood vessels, and is essential for producing cerebrospinal fluid. Signup and view all the answers

What distinguishes the arrangement of neurons in the somatic nervous system from the autonomic nervous system?

The somatic nervous system consists of a single neuron extending from the CNS to skeletal muscle, while the autonomic system involves two neurons in series linking the CNS to the effector. Signup and view all the answers

What is meant by dual innervation in the context of the autonomic nervous system?

Dual innervation refers to organs receiving signals from both the sympathetic and parasympathetic divisions, which have opposing effects. Signup and view all the answers

What are the two major types of neurons in the autonomic nervous system, and where are their cell bodies located?

The two major types are preganglionic and postganglionic neurons, with cell bodies located in the lateral horn of the spinal cord and autonomic ganglia, respectively. Signup and view all the answers

Discuss the role of hypothalamus in autonomic nervous system regulation.

The hypothalamus integrates information from the brainstem and spinal cord, influencing autonomic functions such as heart rate and digestion. Signup and view all the answers

How does the structure of the brain's ventricles facilitate cerebrospinal fluid circulation?

The brain's ventricles are interconnected cavities lined with ependymal cells that aid in the circulation of cerebrospinal fluid. Signup and view all the answers

In what ways do the sympathetic responses prepare the body for challenging situations?

Sympathetic responses increase heart rate, dilate airways, and redirect blood flow away from the digestive system to muscles. Signup and view all the answers

Why is the pia mater described as a delicate layer in terms of its physical characteristics and function?

The pia mater is a thin, delicate layer tightly adherent to the brain that contains small blood vessels and provides structural support. Signup and view all the answers

Study Notes

Spinal Cord

The spinal cord is a long, cylindrical bundle of nerve tissue extending from the brain stem to the lumbar region of the vertebral column.
The spinal cord can be divided into different regions: cervical, thoracic, lumbar, sacral, and coccygeal.
There are 31 pairs of spinal nerves that emerge from the spinal cord.
The spinal cord's diameter increases in the cervical and lumbar regions due to nerve enlargements responsible for supplying nerves to the arms and legs.
The pointed end of the spinal cord is called the conus medullaris and the "horse tail" of nerve roots extending from it is known as the cauda equina.

Meninges

The meninges are three layers of protective connective tissue surrounding the brain and spinal cord.
The outermost and thickest layer is the dura mater, followed by the arachnoid mater and finally the pia mater, which is the innermost layer.
The subdural space lies between the dura mater and arachnoid mater, filled with serous fluid.
Between the arachnoid matter and the pia mater is the subarachnoid space, containing cerebrospinal fluid (CSF) and blood vessels.

Spinal cord structure

The spinal cord contains both gray matter (inner core) and white matter (outer layer).
The white matter can be further divided into columns: dorsal, ventral, anterior, and lateral.
The gray matter consists of sensory and motor neurons, organized into horns: posterior, lateral, and anterior/ventral horns.
The central canal runs through the center of the gray matter.

Organization of neurons in the spinal cord

Sensory neurons enter the spinal cord through the dorsal roots.
Motor neurons exit the spinal cord through the ventral roots.
Cell bodies of motor neurons are located in the horns of the gray matter.
Somatic motor neuron cell bodies are in the anterior horns while autonomic motor neuron cell bodies are in the lateral horns.

Nerve Structure

An axon and its associated Schwann cells are surrounded by the endoneurium.
A bundle of axons enveloped in endoneurium is called a nerve fascicle.
Multiple fascicles are wrapped in a thicker connective tissue called the perineurium.
The epineurium encompasses a group of fascicles, forming a nerve or a spinal nerve.

Spinal Nerve Organization

There are 31 pairs of spinal nerves, corresponding to the 31 segments of the spinal cord.
The count of vertebral bones differs from the pairs of spinal nerves due to C1 emerging from the top of the first cervical vertebra.

The Brain

The brain, weighing approximately 1.5kg, is the central control center of the nervous system.
The brain comprises:
- Forebrain (cerebrum, diencephalon)
- Midbrain
- Hindbrain (pons, medulla oblongata, cerebellum)
The midbrain, pons, and medulla oblongata collectively form the brainstem.

Brainstem

The brainstem connects the spinal cord to the rest of the brain.
The brainstem plays a crucial role in regulating essential bodily functions.

Medulla Oblongata

The medulla oblongata is the most inferior part of the brainstem, directly connecting to the spinal cord at the foramen magnum.
It acts as an autonomic reflex center, regulating vital functions like heart rate, blood pressure, breathing rate, and reflex actions like swallowing, coughing, and sneezing.

Pons

The pons is a bulging structure that serves as a bridge between different parts of the brain.
It contains both longitudinal and transverse tracts, transmitting signals between the cerebrum and cerebellum.
The pons houses a sleep center responsible for regulating rapid eye movement (REM) sleep and has a respiratory center that works in coordination with the medulla oblongata.

Midbrain

The midbrain is the smallest and most superior portion of the brainstem.
It processes sensory information from the eyes, ears, and body, initiating reflex movements of the head, eyes, and body.

Cerebellum

The cerebellum, located inferiorly and posteriorly to the cerebrum, is responsible for coordinating movement, regulating fine motor control, and maintaining balance and posture.

Diencephalon

The diencephalon is a central region of the brain located beneath the cerebrum.
It consists of:
- Thalamus: acts as a sensory relay station and is involved in emotions, mood, and memory.
- Subthalamus: located beneath the thalamus.
- Epithalamus: includes the habenula and pineal gland, located posterior to the thalamus.
- Hypothalamus: located below the thalamus and controls numerous bodily functions, including hormone release, body temperature, hunger, thirst, and sleep.

Cerebrum

The cerebrum is the largest and most superficial part of the brain, responsible for higher-level cognitive functions.
It is characterized by gyri (folds), sulci (grooves), and fissures (deep grooves).
The longitudinal fissure divides the cerebrum into two hemispheres, connected by the corpus callosum.
The lateral fissure separates the temporal lobe from the other lobes.
The central sulcus separates the frontal lobe from the parietal lobe.
The cerebrum is divided into five major lobes: frontal, parietal, occipital, temporal, and insula.

Cerebrum 2

The precentral gyrus is the primary motor cortex, controlling voluntary movements, especially fine motor movements of the hand.
The postcentral gyrus is the primary somatosensory cortex, receiving sensory information from receptors in the body.

Limbic System

The limbic system is a network of structures involved in emotions, memory, and behavior.
It encompasses areas around the corpus callosum and diencephalon, influencing emotional responses, memory, and smell-induced memories.

Meninges (Brain)

The meninges, three layers of protective tissue, also surround the brain.
The dura mater is the outermost, tough, fibrous layer, divided into two parts:
- Periosteal dura: attached to the inner surface of the skull
- Meningeal dura: lying beneath the periosteal dura
The subdural space separates the dura mater from the arachnoid mater.
The arachnoid mater is a thin, delicate layer that resembles cobwebs.
The pia mater is the delicate innermost layer, tightly adhering to the brain surface.### Meninges
Three protective layers of connective tissue surround the brain and spinal cord: the dura mater, arachnoid mater, and pia mater.
The dura mater is a tough, outermost layer.
The arachnoid mater is a delicate middle layer with a subarachnoid space containing cerebrospinal fluid and blood vessels.
The pia mater is a thin, innermost layer that closely adheres to the brain and spinal cord, containing small blood vessels.

Ventricles

Four interconnected cavities within the brain called ventricles are lined with ependymal cells.
The lateral ventricles are the largest, extending into the cerebral hemispheres.
The third ventricle is connected to the lateral ventricles and resembles a bird's head.
The fourth ventricle is located in the brainstem and connects to the central canal of the spinal cord.

Cerebrospinal Fluid (CSF)

CSF is produced mainly by the choroid plexus, composed of specialized ependymal cells, support tissue, and blood vessels.
CSF circulates within the ventricles, central canal of the spinal cord, and subarachnoid space.
It provides protection to the brain and spinal cord from trauma and buoyancy, reducing the weight of the brain and pressure on underlying structures.
CSF composition is similar to blood plasma, but with less protein and a different ionic concentration.

Cranial Nerves

Twelve pairs of cranial nerves, named with Roman numerals, directly emerge from the brain.
Cranial nerves carry sensory information from the body to the brain and motor commands from the brain to the body.
They can be sensory, motor, or mixed neurons, carrying a combination of these functions.

Functional Divisions of the Nervous System

The nervous system is divided into two functional divisions: the autonomic nervous system and the somatic nervous system.

Autonomic Nervous System

The autonomic nervous system controls involuntary functions such as heart rate, digestion, and breathing.
It has two branches: the sympathetic and parasympathetic systems.
The sympathetic nervous system is activated in "fight or flight" situations, increasing heart rate and respiration, while decreasing digestion.
The parasympathetic nervous system is activated in "rest and digest" situations, promoting digestion and energy conservation.

Somatic Nervous System

The somatic nervous system controls voluntary movements of skeletal muscles.
It consists of a single neuron that extends from the central nervous system (CNS) to the skeletal muscle.

Anatomy of the Autonomic Nervous System

The autonomic nervous system is a two-neuron system, with a preganglionic neuron from the CNS to an autonomic ganglion and a postganglionic neuron from the ganglion to the target tissue.
Sympathetic preganglionic neurons originate in the thoracolumbar division (T1-L2).
Parasympathetic preganglionic neurons originate in the craniosacral division (S2-S4 and cranial nerve nuclei).

Dual Innervation of the Autonomic Nervous System

Most target organs are innervated by both the sympathetic and parasympathetic nervous systems, often with opposing effects.
This dual innervation allows for precise control of organ function.
Regulation of heart rate, blood pressure, airways, digestive tract, glands, and pupil size occurs through both nervous system divisions.

Regulation of the Autonomic Nervous System

The autonomic nervous system is primarily regulated by reflexes, automatic responses to stimuli that maintain homeostasis.
The CNS, particularly the cerebrum, hypothalamus, and brainstem, influence autonomic reflex activity, integrating information and coordinating responses.
The hypothalamus plays a central role in integrating information and relaying commands to other brain regions.

CNS Components and their Effect on the ANS

Spinal cord: Regulates reflexes for defecation, urination, erection, and ejaculation.
Brainstem: Controls reflexes for tear production, salivation, coughing, swallowing, digestion, respiration, heart rate, and blood vessel diameter.
Hypothalamus: Integrates information from the brainstem and spinal cord, and relays it to higher brain centers like the cerebrum and limbic system.
Cerebrum and limbic system: Thoughts and emotions can influence the ANS through the hypothalamus, affecting responses like increased blood pressure during anger or salivation when thinking about food.

Spinal Cord

Extends from the foramen magnum to the first or second lumbar vertebrae
Divided into cervical, thoracic, lumbar, sacral and coccygeal regions
31 pairs of spinal nerves emerge from the spinal cord

Spinal Nerve Breakdown

Cervical nerves: 8 pairs
Thoracic nerves: 12 pairs
Lumbar nerves: 5 pairs
Sacral nerves: 5 pairs
Coccygeal nerve: 1 pair

Spinal Cord Diameter

Diameter changes from top to bottom
Cervical and lumbar-sacral regions have enlargements
Enlargements correspond with limb innervation: cervical for arms, lumbar/sacral for legs

Spinal Cord Terminology

Conus medullaris: the pointed end of the spinal cord
Cauda equina: the roots of the spinal nerves

Meninges

Connective tissue covering the spinal cord and brain
Functions:
- Protect central nervous system (CNS) and blood vessels
- Contain cerebrospinal fluid
- Form partitions in the skull

Dura Mater

Outermost, superficial, and thickest meningeal layer
Surrounds the brain and outer layer of spinal nerves
Subdural space: between dura mater and next meningeal layer, containing serous fluid

Arachnoid Mater

Resembles cobwebs
Subarachnoid space: deep to arachnoid mater, containing blood vessels and cerebrospinal fluid

Pia Mater

Gentle/tender layer, deepest meningeal layer
Contains many blood vessels
Sits tightly over the spinal cord and brain

Spinal Cord Grey and White Matter

Grey matter: cortex of brain and nuclei, inner in spinal cord
White matter: nerve tracts, outer in spinal cord

Spinal Cord Column Organization

White matter: dorsal, ventral, anterior, and lateral columns
Grey matter: posterior, lateral, and anterior/ventral horns
Contains commissures

Spinal Cord Rootlets

Rootlets merge to form dorsal and ventral roots
Dorsal and ventral roots merge to form a spinal nerve
Central canal: in the center of the grey matter

Sensory and Motor Nerve Pathways

Sensory nerves travel through dorsal roots
Motor (somatic and autonomic) nerves travel through ventral roots

Motor Neuron Cell Bodies

Found in the horns of the grey matter
Autonomic neurons in the lateral horn
Somatic motor neurons in the lateral horn

Nerve Anatomy

Endoneurium: surrounds each axon and its Schwann cells
Nerve fascicle: a bundle of axons surrounded by endoneurium
Perineurium: surrounds a group of axons or a nerve fascicle (coarser connective tissue than endoneurium)
Epineurium: surrounds a group of fascicles (a nerve or spinal nerve)

Spinal Nerve Organization

31 spinal nerves: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal
30 spinal bones: 7 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal (fused)
C1 nerve emerges from the top of the first vertebra

Brain Overview

Jelly-like mass, weighs 1.5kg
Largest and most complex organ in the body
Approximately 100 billion neurons and a trillion neuroglial cells
Components: forebrain (cerebrum and diencephalon), midbrain, hindbrain (pons, medulla oblongata, cerebellum)
Midbrain, pons, and medulla oblongata form the brainstem

Brain Stem Components

Located below the diencephalon
Connects the spinal cord to the rest of the brain
Includes the midbrain, pons, and medulla oblongata

Medulla Oblongata

Connects directly to the spinal cord at the foramen magnum
Autonomic reflex center maintaining homeostasis
Cardiovascular center: regulates heart rate, force of contraction, blood vessel diameter
Respiratory center: regulates breathing rate and depth
Other reflexes: swallowing, vomiting, hiccupping, coughing, sneezing
Functions are automatic and require no thought

Pons

Bulging structure of the brainstem
"Pons" is Latin for bridge; connects different parts of the brain
Conduction tracts:
- Longitudinal tracts: from spinal cord to higher brain centers
- Transverse tracts: from cerebrum (motor cortex) to cerebellum
Contains a sleep center regulating rapid eye movements during sleep
Respiratory center: works with medulla oblongata's center to regulate respiration

Midbrain

Smallest and most superior part of the brainstem
Receives visual, auditory, and tactile sensory input
Generates reflex movements of the head, eyes, and body (e.g., pupil dilation, lens shape)

Cerebellum

Cauliflower-like structure
Located inferior and posterior in the brain
Outer cortex: grey matter
Inner medulla: white matter
Smaller than the cerebrum
Controls locomotion with the cerebrum (walking, running, etc.)
Regulates fine motor control (writing, using a computer, playing music)
Controls posture and balance

Diencephalon

Includes the thalamus, subthalamus, epithalamus, and hypothalamus

Thalamus

Largest part of the diencephalon
Sensory relay center/gateway for all senses except smell
Regulates mood, memory, and strong emotions (fear, rage)

Subthalamus

Area underneath the thalamus

Epithalamus

Includes the habenula and pineal gland
Posterior to the thalamus

Hypothalamus

Below the thalamus
Maintains homeostasis via the endocrine system
Regulates:
- Heart rate
- Digestive activities (food intake, water balance, thirst)
- Muscles involved in swallowing
- Body temperature (sweating and shivering)
- Sex drive and pleasure
- Mood and emotions
- Sleep-wake cycle

Cerebrum

Makes up most of the brain's mass
Most superficial and superior part of the brain
Gyri: elevated tissue folds
Sulci: grooves
Fissures: deep grooves
Divided into right and left hemispheres by the longitudinal fissure
Lateral fissure separates the temporal lobe from the rest of the cerebrum
Central sulcus separates the frontal lobe from the parietal lobe
Lobes: frontal, parietal, occipital, temporal, insula

Cerebrum 2

Precentral gyrus: primary somatic motor cortex
- Controls voluntary movements, especially fine motor movements of the hand
- Located just in front of the central sulcus (part of the frontal lobe)
Postcentral gyrus: primary somatic sensory cortex (somatosensory cortex)
- Receives messages from somatic sensory receptors in skeletal muscles, joints, and tendons
- Processes these sensations (e.g., touch, temperature, pain)
Corpus callosum: bundle of commissural fibers
- Connects the two cerebral hemispheres
- Ensures the brain works as one unit

Limbic System

Runs through the medial aspect of the left and right cerebral hemispheres and the diencephalon
Surounds the border of the corpus callosum and diencephalon
Involved in memory and known as the "emotional brain"
Expresses emotions through gestures
Can trigger emotional responses or memories through smell
Damage can cause memory impairment

Meninges 2 (brain specific)

Dura mater: fibrous connective tissue
- Periosteal dura: most superficial layer, attached to inner surface of the skull
- Meningeal dura: inner layer, continuous with the dura mater of the spinal cord
- Dural venous sinus: space between periosteal and meningeal dura in some parts of the brain
  - Contains veins that collect blood from the brain and return it to the heart
  - Dural folds: connective tissue partitions that extend deep into the brain, helping to hold it in place and prevent excessive movement
- In some parts, the periosteal and meningeal dura fuse together, no Dural venous sinus present
- Subdural space: contains serous fluid
Arachnoid mater: thin, flimsy, and cobweb-like in the brain

Meninges

The arachnoid mater is located above the subarachnoid space, which contains cerebrospinal fluid and blood vessels.
The pia mater is the deepest meningeal layer, it's a delicate connective tissue layer that contains small blood vessels and sits tightly over the brain.
This layer is not removable.

Ventricles

The brain has four ventricles that are continuous with each other.
The ventricles are lined with ependymal cells.
The largest ventricles are the lateral ventricles of the brain.
The lateral ventricles are continuous with the third ventricle, which resembles the head of a bird from a lateral view.
The third ventricle is continuous with the fourth ventricle, which is located in the brain stem and is continuous with the central canal of the spinal cord.

Cerebrospinal fluid

Most cerebrospinal fluid is produced by the choroid plexus, made up of specialized ependymal cells, support tissue, and blood vessels.
Cerebrospinal fluid protects the brain and spinal cord from trauma and provides buoyancy to the brain, reducing the weight of the brain and pressure on structures under the brain.
The composition of cerebrospinal fluid is similar to blood plasma but contains less protein and has a different ionic concentration.
The cerebrospinal fluid circulates the ventricles, the central canal of the spinal cord, and the subarachnoid space of the meninges.
The cilia of the endymal cells of the ventricles help with the circulation flow.

Cranial nerves

There are 12 pairs of cranial nerves, all named after Roman numerals.
Cranial nerves emerge directly out of the brain and carry information from the brain to the body and back to the brain.
Cranial nerves can be either single or mixed neurons, meaning they can have a sensory, somatic, parasympathetic, or a combination of all three functions.

Functional divisions of the nervous system

The nervous system can be divided into the autonomic nervous system and the somatic nervous system.

Autonomic vs. somatic nervous system

The autonomic nervous system controls functions that are not consciously controlled, such as heart rate, digestion, and breathing.
The somatic nervous system controls voluntary movements.

Somatic nervous system

Effector: Skeletal muscle.
Regulation: Controls all conscious and unconscious movements of skeletal muscle.
Response to stimulation: Skeletal muscle contracts.
Neuron arrangement: One neuron extends from the central nervous system to the skeletal muscle.
Neuron cell body location: Located in the ventral horn of the spinal cord.
Number of synapses: 1 (motor neuron -> skeletal muscle).

Autonomic nervous system

Effector: Cardiac muscle, smooth muscle, and glands.
Regulation: Unconscious regulation, although conscious thought has an influence.
Response to stimulation: Target tissues are stimulated or inhibited.
Neuron arrangement: There are two neurons in series; a preganglionic neuron runs from the central nervous system to an autonomic ganglion, and the postganglionic neuron runs from the ganglion to the effector (target tissue).
Neuron cell body location: Located in the lateral horn of the spinal cord and autonomic ganglion.
Number of synapses: 2 (neuron to neuron then neuron to target tissue).

Sympathetic and Parasympathetic

The autonomic nervous system can further be divided into the sympathetic and parasympathetic nervous systems.

Sympathetic nervous system

Stimulated: Sympathetic nervous system is stimulated in threatening or exciting situations.
Effects: Deeper breathing, increased heart rate, decreased or halted digestion, relaxation of the urinary bladder.
AKA: The 'E' division, as it is stimulated during exercise, excitement, emergency, or embarrassment.

Parasympathetic nervous system

Stimulated: Parasympathetic nervous system is activated to keep the body's energy usage as low as possible (energy preservation).
Effects: Activates digestion, salivation, formation of tears, elimination of feces and urine.
AKA: The 'D' division, as it is stimulated during digestion, defecation, and diuresis (urination).

Sympathetic vs. Parasympathetic responses

The sympathetic and parasympathetic nervous systems often have opposing effects on the same organs.

	Sympathetic	Parasympathetic
Heart	Increased heart rate and blood pressure	Decreased heart rate and blood pressure
Airways	Dilation	Constriction
Blood	Mainly constriction, but vasodilation to skeletal muscles	No effect
Digestion	Decreased motility and secretion, constricted sphincters	Increased motility and secretion, sphincters will relax
Liver	Increased glucose released into the blood
Gall
Glands
Sweat
Pupil
Cellular
Bladder

Anatomy of the autonomic nervous system

The autonomic nervous system is a two-neuron system, with cell bodies located in the lateral horn of the spinal cord and the autonomic ganglion.
The location of the cell bodies along the length of the spinal cord is different for the sympathetic and parasympathetic divisions.
- Sympathetic: Cell bodies are found between T1 and L2 (the thoracolumbar division).
- Parasympathetic: Cell bodies are found between S2 to S4 and cranial nerve nuclei (craniosacral division).

Functional generalisations of the sympathetic and parasympathetic nervous systems

The sympathetic and parasympathetic nervous systems demonstrate dual innervation with opposing effects.
The responses generated by both divisions of the autonomic nervous system regulate:
- Heart rate
- Blood pressure
- Airways in the lungs
- Digestive tract
- Glands (salivary, gastric, lacrimal)
- Pupil of the eye

Regulation of the autonomic nervous system

Autonomic nervous system regulation occurs mostly via reflexes, which are automatic responses to stimuli, and are normally homeostatic.
Autonomic reflex activity is also influenced by the central nervous system, particularly the cerebrum, hypothalamus, brainstem, and a few other parts that control thoughts, actions, and emotions.
- The hypothalamus integrates the information that's coming into it and communicates it to other parts of the brain to execute a response.
- Most autonomic reflexes actually involve a part of the Hypothalamus.

Effect on the ANS

CNS Component	Effect on the ANS
Spinal cord	Autonomic reflex centre which regulates defecation, urination, erection, and ejaculation.
Brainstem	Reflex centre controls tear production, salivation, coughing, swallowing, digestive activities, heart rate and force of contraction, blood vessel diameter, and respiration.
Hypothalamus	Integrates the incoming information from the brainstem and the spinal cord and relays any information that goes to higher centres of the brain such as the cerebrum and limbic system.
Cerebrum & Limbic	Thoughts and emotions can influence ANS functions through the hypothalamus e.g. - Yes, homeostasis would be hugely disrupted as the hypothalamus plays a very significant role in body homeostasis.

Station 2b

The vermis is the part of the cerebellum that connects the two hemispheres of the brain.
The cerebellum is not convoluted but has many branches.
The cerebellum is involved in the coordination of fine motor movements.
In the spinal cord, the white matter is on the outside, and the grey matter is on the inside. In the brain, the white matter is on the inside with the grey matter on the outside.
The grey matter consists of cell bodies, while the white matter consists of myelinated axons.

Case study 1

The temporal lobe was operated on as the hippocampus is located deep to the temporal lobe.
The temporal lobe is involved in motor function, somatic sensory information, input of hearing, and memory.
Short-term memory is mostly stored in the temporal lobe, but long-term memory is distributed throughout the brain.
Muscle memory is related to learning new skills.

Case study 2

Phineas Gage, a railroad worker, had a 6 kg, meter-long pole blasted through his head, passing from under his cheekbone and exiting the top of his cranium just posterior to his hairline.
The rod would have passed through his frontal lobe.
He survived as the more crucial parts of the brain are located in the hindbrain/brainstem.
The frontal lobe is involved in:
- Voluntary motor function
- Motivation
- Planning
- Aggression
- Sense of smell
- Regulation of emotional behaviour and mood
The hypothalamus also plays a role in regulating mood and emotions.
The limbic system and hippocampus, which were preserved, control these functions.

Case study 3

The patient in case study 3 had a problem with their cerebellum.
Testing for fine motor skills, coordination, and distance judgement were used to evaluate the patient.
The patient's failure to develop a properly functioning cerebellum caused these issues.

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Description

This quiz covers the essential information about the spinal cord and its structural components, including its regions and nerve pairs. Additionally, it explores the protective layers of the meninges surrounding the brain and spinal cord. Test your understanding of this crucial aspect of human anatomy!