A&P - Chapter 11: Nervous System

Spinal Cord

Major communication link between the brain and PNS portion below the head, many reflex responses are produced here. It is the nervous tissue running along the vertebral column.

Conus Medullaris

Cone-shaped end of spinal cord.

Cauda Equina

Term for the many branching nerves off the spinal cord.

Meninges

Connective tissue membranes surrounding the spinal cord.

Spinal Cord Meninges

Superficial to Deep:

Outside layer of bone: periosteum

0\.5) Epidural space

1) Dura mater

1\.5) Subdural space

2) Arachnoid mater

2\.5) subarachnoid space

3) Pia mater

Dura Mater

Thickest layer of meninges, often referred to as the thecal sac as it surrounds the spinal cord.

Arachnoid Mater

Thin, cobweb-like layer of meninges.

Pia Mater

Layer of meninges right up against the spinal cord.

Subarachnoid Space

Large space between meninges, allowing movement and containing blood vessels and cerebrospinal fluid.

Spinal Anesthesia

Drugs to block lower body pain are inserted into subarachnoid space that extends below end of spinal cord.

Spinal Tap

Removal of a sample of cerebrospinal fluid (CSF) from the subarachnoid space.

White Matter

Forms columns or funiculi. Each column can be divided further into tracts, fasciculi or pathways (tracts must be ascending or descending).

Gray Matter

Forms horns and contains the central canal, roots, and dorsal root ganglion.

Central Canal

Opening along center of the spinal cord, containing CSF.

Roots

Bundles of axons (nerves) extending out from horns and into PNS.

Dorsal Root Ganglion

Bundle of cell bodies of sensory neurons.

Sensory Neurons

Dorsal Root

Somas of Sensory Neurons

Dorsal Root Ganglion

Somas of Interneurons

Posterior Horns

Soma

Cell body of neurons.

Somas of Motor Neurons

Anterior Horns

Motor Neurons

Ventral Root

Reflex

Stereotypic, unconscious, involuntary response to a stimulus.

Stereotypic

Reflex where the response is always essentially the same.

Unconscious

Reflex where the person does not need to be aware that the response happening.

Involuntary

Reflex where the response happens without the person choosing for it to happen.

homeostasis

Reflexes maintain _____________.

Types of Reflexes

1) Somatic Reflexes

2) Autonomic Reflexes

Somatic Reflexes

Involve skeletal muscles, used for avoiding pain and falling.

Autonomic Reflexes

Involve blood and organs, used for maintaining blood pressure and CO2 levels.

Reflex Arc (Simple)

1) Receptor

2) Sensory Neuron

3) Interneuron

4) Motor Neuron

5) Effector

Stretch Reflex

When muscles contract in response to receptors known as muscle spindles detecting excessive stretching (Knee-Jerk Reflex).

Golgi Tendon Reflex

Where muscles relax in response to receptors known as Golgi tendon organs detecting excessive stretching of a tendon. Ex.) Weightlifters, dropping weights

Withdrawal Reflex

(Flexor Reflex) Where a limb or part of the body is removed from a painful stimulus.

Nerve

Collections of axons, Schwann cells, and connective tissue in the PNS.

Axon

nerve fiber

nerve

There are multiple layers of CT around each _____.

Dermatome

Area of skin supplied with sensation by a pair of spinal nerves.

31

There are ___ pairs of spinal nerves.

Dermatomal Map

What is this?

roots

Every nerve splits into ventral and dorsal _____ at the spinal cord.

rootlets

The roots often further split into _______.

Types of Rami

1) Dorsal Ramus

2) Ventral Ramus

Plexus

A “braid” of nerves connecting and dividing.

plexus

It is common to say a nerve arises from a _______ instead of the spinal cord since it’s going to mix and mingle with other nerves anyway.

coccygeal

The _________ plexus is very small and often overlooked.

Brain

The complex control center located in the cranial cavity (within the skull). It’s like a computer in it’s ability to process information. Has gray and white matter.

Nuclei

Spots of gray matter which regulate various bodily activities.

Tracts

Large areas of white matter that bring info to the spinal cord or other areas of the brain.

Sections of the Brain

1) Brainstem

2) Cerebellum

3) Diencephalon

4) Cerebrum

Brainstem

Most inferior part of the brain, looks like the top of the spinal cord, connects the spinal cord & cerebellum to the rest of the brain, has many ascending & descending tracts.

Sections of Midbrain

1) Medulla Oblongata

2) Pons

3) Midbrain

Medulla Oblongata

Continuous with the spinal cord.

Regulates: heart rate, blood vessel diameter, breathing, swallowing, vomiting, coughing, sneezing, hiccuping, balance, and coordination.

Pons

Means “bridge”.

Regulates: Breathing, swallowing, balance, chewing, and salivation.

Midbrain

Regulates: eye coordination, pupil diameter, lens shape, and body movements.

Cerebellum

Portion of brain posterior to the brainstem, “little brain”.

Regulates: balance, posture, eye movements, locomotion, and fine motor coordination.

Parts of the Cerebellum

1) Flocculonodular Lobe

2) Vermis

3) 2 Lateral hemispheres

Folia

Ridges on the cerebellum.

Primary Fissure

Deep ridge splitting each lateral hemisphere.

Pieces of Lateral Hemisphere

1) Anterior Lobe

2) Posterior Lobe

Cortex

Gray matter on edges, that follows the folia.

Arbor Vitae

“Tree of Life” White matter that has connecting tracts which resemble a tree or leaf veins.

Diencephalon

Portion of the brain between the brainstem and the cerebrum.

Sections of Diencephalon

1) Thalamus

2) Subthalamus

3) Epithalamus

4) Hypothalamus

Thalamus

(Sensory Relay Center) Largest part of the diencephalon, has large right and left sections connected by a small interthalamic adhesion or intermediate mass. Has many nuclei, all sensory info, except smell passes through before the cerebrum. Interacts with brain areas which regulate skeletal muscle control.

Epithalamus

Small area superior and posterior to the thalamus.

Parts of Epithalamus

1) Habenula

2) Pineal Gland

Habenula

Area of brain involved in responses to smell as well as emotional responses to odor.

Pineal Gland

Pinecone-shaped endocrine gland, controls puberty & influences sleep-wake cycle and other body rhythms.

Hypothalamus

Most inferior portion of diencephalon, is a collection of nuclei that affect a HUGE range of bodily functions.

Parts of Hypothalamus

1) ANS

2) Endocrine

3) Limbic System

4) Basic Body Functions

ANS

Helps regulate heart rate, blood vessel diameter, urine release, and movement of food in digestion.

Endocrine

Connects the pituitary gland to brain via infundibulum.

Infundibulum

Regulates release of pituitary hormones.

Limbic System

Parts of brain regulating mood, motivation, emotions, sexual pleasure, etc. Also, contains mammillary bodies.

Mammillary Bodies

Nuclei that are externally visible on the hypothalamus and are involved in odor emotion responses, reflexes to smells, and memory.

Basic Body Functions

(Hypothalamus) Sweating, shivering, thirst, hunger, sexual arousal. Also, has suprachiasmatic nucleus.

Suprachiasmatic Nucleus

Circadian Rhythm

Cerebrum

Most superior portion of the brain, though it also wraps around the diencephalon and some of the brainstem.

intelligence

The size of the cerebrum is not connected with __________, but rather in relation to overall body size.

Parts of Cerebrum

1) Right & Left Hemispheres

2) Multiple Lobes

3) Deeper Nuclei & systems

Gyrus

Fold or wrinkle on surface of cerebrum.

Sulcus

(Fissure) Groove between the gyri.

Frontal Lobe

Voluntary motor functions, motivation, aggression, sense of smell, and mood.

Parietal Lobe

Receives and evaluates most sensory info such as taste, touch, pain, temperature, balance, etc.

Occipital Lobe

Receives and evaluates visual input.

Temporal Lobe

Receives and evaluates smell and hearing input, and also plays a role in memory. Also active during thought and judgement.

Basal Nuclei

Group of nuclei which function together, located throughout the cerebrum, diencephalon, and midbrain. They regulate control of motor functions.

Limbic System

A collection of nuclei and cortexes of the cerebrum and diencephalon that function together. Together, these areas of gray matter help regulate memory, reproduction, nutrition, and emotional response to sensory information.

diencephalon

The Limbic System surrounds the ____________.

Brain Meninges

1) No epidural space (no room in the cranial cavity)

2) Dura mater layer: periosteal layer

3) Dura mater layer: meningeal layer

Dura Fold

Sections of the meningeal layer of dura mater that dive into the fissures of the cerebrum.

Sinuses

Spaces that form between the two dural layers, all veins draining blood from the brain empty into these (dural veneous fold).

Ventricles

Large cavities in the brain which contain cerebrospinal fluid (CSF).

central canal

All the ventricle cavities are connected to each other as well as to the _____________ of the spinal cord.

Apertures

Three openings which connect to the subarachnoid space of the brain and spinal cord.

Septum Pellucidum

Very thin wall between the two lateral ventricles.

Interventricular Foramina

Think tubes connecting lateral ventricles to third ventricle.

Cerebral Aqueduct

Narrow canal connecting third ventricle with fourth ventricle.

Cerebrospinal Fluid

Fluid filling the ventricles, central canal, and subarachnoid space. Surrounds all brain and spinal NS tissue and acts as a cushion, and provides a few nutrients. It is similar to blood without any proteins.