Anatomy Exam #3

**Nervous System**

1. Includes
- All neural tissue in body (neurons/glial cells)

**Nervous System Functions**

1. Collect information
- Monitor external and internal changes
- Sensory input from PNS
2. Process and evaluate information
- Processes sensory input
- Determines response
3. Respond to information
- Dictates response by activating effector organs

**Sensory Nervous System**

1. Contains receptors
2. Transmits information from receptors to CNS
3. Split into three divisions

* Somatic
* Visceral
* Special senses

**Somatic Sensory**

1. Sensory nervous system
2. Receives sensory information from
- Skin
- Fascia
- Joints
- Skeletal muscles
- Special senses
3. Free nerve endings in almost all body tissues
4. Includes receptors for
- Touch
- Pain
- Pressure
- Vibration
- Temperature
5. Proprioception

**Visceral Sensory**

1. Sensory nervous system
2. Receives sensory information from viscera
3. Sensations from organs

* Digestive tract


* Urinary tract
* Reproductive organs


4. Only stretch and temperature

**Motor Nervous System**

1. Transmits information from CNS to rest of body
2. Sends motor information to effectors
3. Split into two divisions
- Somatic
- Autonomic

**Somatic Motor**

1. Motor nervous system
2. “Voluntary” nervous system
- We can control
3. Innervates skeletal muscle
- Contraction

**Autonomic Motor**

1. Motor nervous system
2. "Involuntary" nervous system
- We cannot control
3. Innervates (contraction)
- Cardiac muscle
- Smooth muscle
- Gland secretion
4. Subdivides
- Sympathetic
- Parasympathetic

**Proprioception**

1. Part of somatic sensory nervous system
2. Sense of body in space in
- Skin
- Body wall
- Limbs

**Special Senses**

1. Part of somatic sensory nervous system
2. Includes
- Vision
- Taste
- Hearing
- Balance
- Smell

**Sympathetic System**

1. Part of autonomic motor
2. Involuntary
3. Widespread, long-lasting mobilization
4. Effects:

* Increase heart rate, respiration and adrenaline
* Pupils dilate
* Liver releases sugars (energy) into the blood
* Digestion slows
* Blood redirected (to skeletal muscles/brain)
* Cold skin


4. Activates fight or flight
5. Thoracolumbar (emergencies, exercise, excitement)

**Parasympathetic System**

1. Part of autonomic motor
2. Highly localized and shorter lived
3. Effects

* Heart rate and respiration slows
* Blood flow to digestive system increases
* Pupils constricted


4. Resting and digesting
5. Craniosacral (normal, everyday functioning, housekeeping)

**Nervous Tissue**

1. Two types of cells
- Neurons
- Glia

**Neurons**

1. Found in nervous tissue
2. AKA nerve cells
3. Transmit electrical signals
4. Excitable

**Glia**

1. Found in nervous tissue
2. AKA nerve glue
3. Supporting cells
4. Not excitable

What is the structure of a neuron?

1. Includes
- Dendrites
- Soma
- Axon
- Axon terminal
- Myelin sheath

**Dendrites**

1. Receive signal from other neurons
2. Transmit signal to cell body
3. Dendrites are smaller projections from soma
4. The more dendrites on a neuron, the more impulses that neuron can receive from other neurons

**Soma**

1. AKA cell body
2. Receives signal from dendrites
3. Transmit signal to axon
4. Contains
- Nucleus
- Cytoplasm
- Organelles

**Axon**

1. AKA long cell process
2. Receives signal from soma
3. Transmits signal to axon terminal
4. Lined with myelin sheath
5. Generate impulses
6. Conduct signal away from the cell body

**Axon Terminal**

1. Receives signal from axon
2. Transmits signal to the next neuron

**Myelin Sheath**

1. Made of glial cells
2. Insulates/surrounds axon
3. Helps propagate signal
- Speeds up time

Signal Pathway

1. Dendrite
2. Cell body
3. Axon
4. Axon terminal

Synapse

1. A site where an axon connects with another cell
- Another neuron cell or muscle and gland cells
2. Two types
- Chemical synapses
- Electrical synapses

Chemical Synapses

1. Most numerous
2. Use neurotransmitters

Electrical Synapses

Rely on flow of ions at gap junctions

**Glia of CNS**

1. Support and protect neurons
2. Four types
- Ependymal cells
- Microglia
- Oligodendrocytes
- Astrocytes

**Ependymal Cells**

1. Glia of CNS
2. Helps produce CSF

**Microglia**

1. Glia of CNS
2. Defense

**Oligodendrocytes**

1. Glia of CNS
2. Myelinate axons of CNS

**Astrocytes**

1. Glia of CNS
2. Most common
3. Blood-brain barrier

**Glia of PNS**

1. Support and protect neurons
2. Two types

* Schwann cells
* Satellite cells

**Schwann Cells**

1. Glia of PNS
2. Myelinate axons of PNS

**Satellite Cells**

1. Glia of PNS
2. Found in ganglia
3. Surround neuron cell bodies

Ganglia

Collections of neuron cell bodies outside of CNS

**Nerves**

1. A collection of axons in the PNS
2. Axons are arranged in parallel and wrapped in connective
tissue
3. A nerve can contain
- Myelinated and/or non-myelinated
- Sensory and/or motor axons

Nerve Structure

1. Each axon is surrounded by myelin sheath
- Schwann cells
2. Groups of axons are nerve fascicles
3. Groups of fascicles are a nerve
4. Parts include
- Endoneurium
- Perineurium
- Epineurium

**Endoneurium**

Surrounds axon and myelin sheaths

**Perineurium**

Surrounds fascicle

**Epineurium**

Surrounds entire nerve

Multiple Sclerosis

1. Progressive demyelination of neurons in CNS with destruction
of oligodendrocytes (glia)
2. Interrupts conduction of nerve impulses
3. Inflammation leads to scarring and permanent problems

**Central Nervous System**

1. AKA CNS
2. Includes
- Spinal cord
- Brain
- Neural tissue
- Blood vessels
- Connective tissues
3. Responsible for integrating, processing, and coordinating sensory data and motor commands
4. Where higher functions occur
- Intelligence
- Memory
- Learning
- Emotion

**Peripheral Nervous System**

1. AKA PNS
2. Includes
- Cranial nerves
- Ganglia
- Spinal nerves
- Nerves OUTSIDE spinal cord and brain
3. Link all regions of body to CNS
4. Delivers sensory information to CNS
5. Carries motor commands to peripheral tissues and systems

**Functions of the Brain**

1. Controls
- Heart rate
- Respiration
- Blood pressure
2. Maintains homeostasis
3. Innervation of
- Head
- Neck
- Viscera
4. High level tasks
- Intelligence
- Consciousness
- Memory
- Emotion
- Behavior

**What are the main parts of the brain?**

1. Cerebrum
2. Diencephalon
3. Cerebellum
4. Brian stem

Gray Matter

1. On the outer part of the brain
- Cerebellar and cerebral cortex
2. Innermost regions
- Cerebral nuclei
3. Made up on
- Unmyelinated neurons
- Neuron cell bodies

**White Matter**

1. Deep to the cortex of brain
2. Made of myelinated axons
3. Contains corpus callosum

* Connects the left and right hemisphere of the brain

**Diencephalon**

1. Surrounded by cerebral hemispheres
2. Contains 3rd ventricle
3. Lateral walls = thalamus
4. Floor = hypothalamus
5. Roof = epithalamus

**Thalamus**

1. Forms lateral walls of the 3rd ventricle
2. Filters somatosensory, visual, and auditory info
- Except smell
3. Any part of the brain (sensory or not) that communicates with
cerebral cortex must go through thalamus

**Hypothalamus**

1. Main visceral control center of the body
2. Regulates many activities
- Controls autonomic nervous system
- Regulates body temperature
- Regulates hunger/thirst
- Regulates sleep-wake cycles
- Controls endocrine system
- Controls emotional responses
- Formation of memory

**Epithalamus**

1. Forms roof of third ventricle
2. Includes pineal gland
- Secretes melatonin for circadian rhythm

Cerebrum

1. Divided into 2 halves
- Left and right hemispheres
2. Each hemisphere is divided into 5 distinct lobes
- Frontal
- Parietal
- Occipital
- Temporal
- Insula

**Gyri**

1. Ridges of brain tissue
2. Allows for more cerebral cortex to fit in cranial vault
3. Includes
- Precentral gyri
- Postcentral gyri

**Sulci**

1. Grooves between gyri
2. Includes
- Central sulci
- Parieto-occipital sulci
- Lateral sluci

**Cerebral Functions (Cerebrum)**

1. Intelligence
2. Complex thinking
3. Regulates temperature
4. Movement
5. Three types of functional areas

* Sensory; conscious awareness of sensation
* Association; integrate information
* Motor; voluntary motor functions

**Primary Somatosensory Cortex**

1. Receives information from somatic senses
- Touch
- Pressure
- Vibration
- Pain
- Proprioception
2. Enables conscious awareness of senses
3. Located in postcentral gyrus

**Primary Visual Cortex**

1. Posterior/medial occipital lobe
2. Receives visual info from retina of eye

**Primary Auditory Cortex**

1. In temporal lobe
2. Receives and processes auditory information from inner ear

**Primary Motor Cortex**

1. Located in precentral gyrus
2. Control voluntary skeletal muscle activity
3. Other motor areas include Broca’s

**Broca's Area**

1. Motor speech area
2. Controls motor movements for speech
3. If damaged

* Can comprehend
* Can not speak

**Wernicke's Area**

1. Multimodal association area
2. Recognition and understanding of speech
3. If damaged

* Can speak
* Can not comprehend

**Corpus Callosum**

1. White matter of cerebrum
2. Largest, most visible band of commissural fibers
- Fibers that connect two hemispheres

Association Fibers

Short fibers that connect regions in the same hemisphere

**Cerebral Nuclei**

1. AKA deep gray matter
2. AKA basal nuclei/ganglia
3. Paired masses
4. Involved in motor control
5. Start, stop and regulate the intensity of voluntary
movements

**Brain Stem**

1. Connects cerebrum and spinal cord
2. Start of cranial nerves for innervation of the face and head
3. Autonomic and reflex centers needed for survival
4. Composed of
- Midbrain
- Pons
- Medulla oblongata

**Midbrain**

1. Located between diencephalon and pons
2. Part of brain stem
3. Internal cavity is cerebral aqueduct

* Part of brain ventricles

Tectal Plate

1. Midbrain
2. Site for reflexes

Superior Colliculi

1. Midbrain
2. Visual reflexes

Inferior Colliculi

1. Midbrain
2. Responds to sound

**Pons**

1. Part of the brainstem
2. Located between midbrain and medulla
3. Separated from cerebellum by fourth ventricle

**Medulla Oblongata**

1. Part of brain stem
2. Most caudal part of brain stem
3. Continuous with spinal cord
4. Pyramids carry voluntary motor output from cerebrum to spinal cord
5. Fibers “decussate”/crossover
- Left brain controls right side of body
- Right brain controls left side of body

**Cerebellum**

1. Connected to brainstem
2. Functions
- Fine-tunes/tweaks body movements
- Coordinates body movements
- Maintain posture and equilibrium
- Balance
3. Two hemispheres connected by vermis
4. Contain folia
5. Outer cortex is gray matter
6. White matter is arbor vitae
7. Receives information from cerebrum on movements planned
8. Compares planned movements with current body position
9. Sends instructions back to cerebral cortex to readjust/refine motor commands
10. Makes up 11% of mass of brain

Folia

1. Cerebellum
2. Leaflike folds that increase surface area

**Arbor Vitae**

1. AKA tree of life
2. White matter in cerebellum

**Limbic System**

1. Involved with
- Emotion
- Motivation
- Creating, storing, retrieving memories
2. Includes
- Cingulate gyrus
- Hippocampus
- Amygdala
3. Connected by fornix

**Cingulate Gyrus**

1. Limbic system
2. Emotional response

**Hippocampus**

1. Limbic system
2. Stores memory

**Amygdala**

1. Limbic system
2. Processes fear

**Meninges**

1. Membranes that surround and protect the brain
2. Cover and protect CNS
3. Enclose and protect blood vessels to CNS
4. Contain and circulate cerebrospinal fluid
5. Includes
- Dura matter
- Pia matter
- Arachnoid matter

Cerebrospinal Fluid

Cushions the brain

Blood Brain Barrier

Protects brain from exposure to toxins

**Pia Mater**

1. Innermost meninges layer
2. Follows curves of brain,
3. Very delicate
4. Lots of blood vessels

**Arachnoid Mater**

1. Middle meninges layer
2. Looks like spiderweb
3. Includes subdural space that can fill with fluid or blood due to trauma/disease

Subarachnoid Space

1. Weblike threads that attach arachnoid mater to pia mater
2. Filled with CSF

**Dura Mater**

1. Outermost meninges layer
2. AKA hard mother
3. Two layers of dense fibrous connective tissue

* Meningeal
* Periosteal


4. Spinal dural sheath

**Dural Venous Sinuses**

1. Drain blood from brain
2. Drains into internal jugular veins
3. Widenings (spaces) between the periosteal layer and meningeal layer of dura mater
4. Major ones

* Superior sagittal sinus
* Straight sinus
* Transverse sinus
* Sigmoid sinus

**Brain Ventricles**

1. Four interconnected cavities or expansions within brain for circulating CSF
2. Lateral ventricles are the most superior
3. Lateral ventricles communicate with third ventricle via interventricular foramen
4. Third ventricle drains into fourth ventricle via cerebral aqueduct
5. Fourth ventricle connects to central canal of spinal cord

Interventricular Foramen

The lateral ventricles of the brain communicate with the third ventricle via this

**Cerebral Aqueduct**

1. The third ventricle drains into fourth ventricle via this
2. Connects the ventricles

**Cerebrospinal Fluid**

1. AKA CSF
2. Brain and spinal cord “float” in CSF
3. Functions
- Prevents damage/crushing
- Resists compressive forces
- Cushions against trauma
- Feeds brain
- Removes wastes
- Carries chemical signals
4. Made in choroid plexuses
5. Flows through ventricles and into subarachnoid space
6. Flows through subarachnoid space
7. Absorbed into dural venous sinuses
8. 500 ml/day is processed/circulated

**Arteries of Head and Neck**

1. Right/left common carotid arteries both ascend into the neck and head and divide into internal/external carotid arteries
2. Internal and external carotid arteries feed the head, brain and orbital regions

**Blood Supply for Brain**

1. Internal carotid artery divides into anterior/middle cerebral arteries
2. Anterior cerebral artery joins anterior communicating artery
3. Middle cerebral artery supplies parts of temporal and parietal lobes
4. Right/left vertebral arteries merge to become basilar artery, which divides into posterior cerebral arteries
5. These are connected by posterior communicating arteries
- 80% of cerebrum

**Cerebral Arterial Circle**

1. AKA Circle of Willis
2. Anastomosis to protect brain’s blood supply
- Allows re-routing of blood flow
3. Formed by
- Posterior cerebral arteries (L/R)
- Posterior communicating arteries (L/R)
- Internal carotid arteries (L/R)
- Anterior cerebral arteries (L/R)
- Anterior communicating artery

**Spinal Cord (CNS)**

1. Functions

* Sensory and motor innervation of body
* Two-way conduction pathway for signals between body/brain
* Major center for reflexes


2. Extends from foramen magnum to level L1 or L2
3. **31 pairs of spinal nerves (PNS)**
4. Cervical/lumbar enlargements for nerves of upper/lower limbs
5. Inferior end of SPINAL CORD conus medullaris
6. Inferior end of VERTEBRAL CANAL cauda equina
7. Filum terminale

**Conus Medullaris**

1. Inferior end of spinal cord
2. Ends at L1 vertebra in adults

* Vertebrae growth outpaces spinal cord


3. Ends around L4 in kids

**Cauda Equina**

Nerve roots at inferior end of vertebral canal

**Filum Terminale**

1. Long filament that extends past conus medullaris
2. Extends from conus medullaris to coccyx
3. Acts as a tether

**Denticulate Ligaments**

Anchors spinal cord to dura mater

Epidural Space

1. Pocket in spinal cord
2. Filled with fat and veins

Arachnoid Granulations

1. AKA villi
2. Project through dura mater into superior sagittal sinus
3. Act as one-way valves to control passage of CSF into sinuses

**Spinal Nerves**

1. PNS
2. 31 pairs
3. Dorsal and ventral roots merge to form spinal nerve
4. Has both sensory and motor axons
5. Exits vertebral column at intervertebral foramina
6. Immediately splits into dorsal and ventral rami
7. Cervical spinal nerves emerge superior to their respective vertebrae

* C1 spinal nerve emerges superior to C1 vertebra


7. Thoracic to coccygeal spinal nerves emerge inferior to respective vertebrae

* C8 spinal nerve emerges inferior to C7 vertebra