Physiological Psychology Final Exam

Two Divisions of the Nervous System

• Central Nervous System/CNS

• Peripheral Nervous System/PNS

Central Nervous System (CNS)

brain and spinal cord

Peripheral Nervous System (PNS)

all the nerves outside of the brain and spinal cord

Divisions of the PNS

• Somatic

• Autonomic

Somatic Division

voluntary subdivision of the PNS

Autonomic Division

regulates involuntary bodily functions. Broken up into the sympathetic and parasympathetic divisions

Sympathetic Division

Division of the autonomic nervous system commonly known as the “fight or flight” division

Parasympathetic Division

division of the autonomic nervous system commonly known as the “rest and digest” division

Efferent Neurons

motor and outgoing

Afferent Neurons

Sensory and incoming

Forms of Protection for the CNS

• Blood-Brain Barrier

• Meninges

• Bones

Divisions of the adult human brain

• Hindbrain

• Midbrain

• Forebrain

Substructures of the Hindbrain

• Myelencephalon

  • Medulla

• Metencephalon

  • Pons

  • Cerebellum

Substructures of the Midbrain

• Mesencephalon

  • Tectum

  • Tegmentum

Substructures of the Forebrain

• Diencephalon

  • Thalamus

  • Hypothalamus

• Telencephalon

  • Cerebral Cortex

  • Basal Ganglia

  • Hippocampus

  • Amygdala

Frontal Lobe

• Precentral Gyrus

• Superior, middle, inferior gyri

• Central Sulcus

Parietal Lobe

• Superior Parietal Lobule

• Inferior Parietal Lobule

Occipital Lobe

• Parieto-occipital Sulcus

• Calcarine Fissure

• Cuneus

Temporal Lobe

• Lateral Sulcus

• Superior Temporal Gyrus

• Middle Temporal Gyrus

• Inferior Temporal Gyrus

Meninges

• Dura Mater

• Arachnoid Mater

• Pia Mater

Ventricles

contain cerebral spinal fluid

Neurons

funcional cellular unit; transmit information via action potential & neurochemical release

Glia

provide structural and metabolic support for neurons (ex. modulate, support, and insulate neurons with myelin sheaths)

Macroglia

• Astrocyte (CNS/PNS) (Physical and Nutritional Support)

• Oligodendrocyte (CNS) (Myelin/Guidance)

• Schwann Cell (PNS) (Myelin/Guidance)

• Satelite Cell (PNS) (Physical Support)

Ependymal Glia

line the ventricles; only present in the CNS

Microglia

Present in the CNS and PNS; function in tissue repair, debris removal, and defense

Gray Matter

unmyelinated neurons and parts of neurons. Divided into “horns” (dorsal and ventral); some axons but mostly cell bodies

White Matter

myelinated parts of neurons and glia, surrounds central gray matter

Planes of Section of the Brain

• Coronal Section

• Sagittal Section

• Horizontal Section

Human Brain Orientation

“hinged” horizontal to vertical at brainstem

Sheep Brain Orientation

Differences in Cortical Folding

• Skull imposes size limits on cerebral cortex

• Overcome by folding into sulci (valleys) and gyri (hills)

• Increases surface area, allowing for more compex processes

Lissencephalic

“smooth brain”

Steps in Histologic Preparation of Tissue

1) Fixing

2) Processing

3) Embedding

4) Slicing

5) Staining

Fixation

1) Blood is drained from the body (by means of saline)

2) Fixative solution (usually formalin) is pumped into vascular system to replace remaining fluid

3) The above steps ultimately stabilize the tissue, disable intrinsic molecules and enzymes to prevent degradation, and increase tissue strength for further processing

Processing

(does not occur when using a vibratome and is optional with cryostat)

1) Embedding in paraffin/wax (for microtome), or

2) Treatment with sugars to prevent cell damage during freezing for the cryostat

Slicing

1) Vibratome, can section unprocessed tissue

2) Cryostat is relatively fast and does not require embedding

3) Microtome provides high quality for thin sections/high mag resolution

Staining

1) Nissl stain provides good general tissue contrast, stains cell bodies

2) Myelin stains affect white-matter only (ex. Luxol blue)

3) Golgi/Silver stains highlight just a few neurons in full detail

Nissl Stain

Luxol Blue Stain

Golgi (aka Silver) Stain

Staining with Cresyl violet - Nissl

• Hydration helps the stain fix in the tissue because cell bodies are full of water

• Dehydration with ethanol solutions help differentiate the Nissl stain by decoloring high myelinated areas of the brain

  • Done from less (70%) to more concentrated (100%) to avoid damaging the tissue due to dramatic changes in the environment where the tissue was previously exposed (distilled water and cresyl violet)

Epidural Space

Area outside of the meninges, mostly adipose tissue. Typically used to provide pain relief for the lower body (common for childbirth)

Subarachnoid Space

Area between the arachnoid mater and pia mater, contains CSF. Typically used to provide total body numbness/pain relief or check for bacteria in the CSF.

Cervical Vertebrae

8 (C1 - C8); send & receive info from the head, neck, shoulders, diaphragm

Thoracic Vertebrae

12 (Th 1 - Th 12); send & receive info from the trunk muscles, chest wall, and organs

Lumbar Vertrebrae

5 (L1 - L5); send & receive info from lower back, legs, feet.

Sacral Vertebrae

5 (S1 - S5); send & receive info from bowel, bladder, and sexual functions

Dermatome

an area of skin/the body associated with a single spinal cord segment (sensory and motor region)

Quadriplegia

loss of feeling in most of the body

Paraplegia

loss of feeling in the lower extremities

Decussation

the crossing of nerve fibers or tracts from one side of the body to the other (intersection for an X-shape)

Dorsal Root

sensory axons and interneuron cell bodies, ascending

Ventral Root

motor cell bodies, descending. Carries motor information from neurons to body’s muscles

Dorsal Horn

receives ascending sensory info from the body and carries this info to the brain

Ventral Horn

contains the cell bodies of the motor neurons. Receive input from other parts of the brain and spinal cords and send signals down their axons

Tract

a bundle of nerve fibers within the CNS that connects one area to another

Multiple Sclerosis (MS)

• Preferentially affects cervical spinal cord (dorsal areas)

• Body’s immune cells attacking myelin leading to inflammation around nerves

• Common symptoms: ascending numbness, starting in feet, bilateral hand numbness, numbness on one side of the body

Amyotrophic Lateral Sclerosis (ALS)

• Loss of lower motor neurons in the ventral horn

• Degredation of lateral column pathways in spinal cord

• Muscle atrophy

• No changes in intellect or memory

Meningitis

inflammation of the meninges. Symptoms include: headache, stiff neck, high fever. Massive immune response in CNS leads to swelling and cell death. Detected through a spinal tap to check for bacteria in the CSF. Also known as “Dorm Disease”

Encephalitis

inflammation of the brain tissue, often caused by an infection (like a virus) or sometimes the body’s immune system attacking the brain.

Spinal Segment

region associated with one vertebra and one dorsal/ventral nerve pair

Dorsal Route

• Information comes from the body to the spinal cord via the dorsal root into the rootlets

• Dorsal rootlets enter the cord at the posterolateral sulcus

Ventral Route

• Information goes from the spinal cord to the body through the ventral rootlets into the ventral root

• Ventral rootlets enter the cord at the anterolateral sulcus

Dorsal Root Ganglion Cells

“pseudounipolar neurons”, meaning they have one long axon with two branches

• One branch extends peripherally (out of the CNS) to the muscles/skin

• Ohter branch extends centrally (into the CNS) towards the spinal cord

Dorsal Column - Medial Lemniscus (touch)

• Concious touch and proprioception from lower body (gracile) and upper body (cuneate)

• Ascending (sensory) pathway

• Somatosensory neurons in the dorsal root ganglia send axons into the dorsal column

  • These synapse which crosses (decussates) in the MEDULLA, slightly above motor crossing

Spinothalamic Tract

• Ascending (sensory) Pathway

  • Lateral - Pain and thermal sensations

  • Anterior - light touch

• 1st Synapse: Neurons in the substantia gelatinosa send axons that decussate (cross midline) and travel down the spinal cord

  • Sensory crossing at the level of entry in spinal cord (no bundled decussation of tract)

Corticospinal Tracts

• Descending (motor) Pathway

• Principal pathway for the production of skilled volitional movements

• Pyramid: corticospinal fibers forming a prominent fiber bundle on the ventral surface of the MEDULLA

  • Motor (pyramidal) decussation in Medulla, slightly below sensory decussation and visible “pyramids”

• Upper motor neuron axon (in primary motor cortex) synapses with a cell body of a lower motor neuron in the ventral horn of the spinal cord

• Lower motor neurons leave spinal cord through the ventral route to innervate muscles

General Functions of the Brainstem

• Conduit Functions - passageway for information flow

• Integrative Functions - integration point for information between higher and lower order structures

• Cranial Nerve Functions - receive sensory and sends motor information to/from the head and vital organs

Divisions of the Brainstem

Key Ventral Structures of the Medulla

• Superior Olive

  • Auditory perception

• Inferior Olive

  • Cerebellar motor learning

• Pyramids

  • Corticospinal tract

Key Dorsal Structures of the Medulla

• 4th Ventricle

• Cuneate Nucleus

  • Upper Body

• Gracile Nucleus

  • Lower Body

Key Ventral Structures of the Pons

• Pontine Nuclei

  • Relay cortical input to the cerebellum and spinal cord

• Basal Pons

  • “Bulge” that dominates this surface. Contains cell bodies of pontine nuclei the “middle men” in communication of motor information from cortex to cerebellum

• Trapezoid Body

  • At junction of medulla and pons

  • Bundle of fibers involved in auditory processing

Key Dorsal Structures of the Pons

• Cerebellar Peduncle

  • large white matter bundles connecting cerebellum to brainstem

• Cochlear Nucleus

  • Auditory info to inferior colliculus

  • Fibers = trapezoid body

Key Ventral Structures of the Midbrain

• Cerebral Peduncle

  • Large white matter stalks; descending motor fibers from cortex to the brainstem

Key Dorsal Structures of the Midbrain

• Superior Colliculi

  • Process visual info from retina

  • Detect and localize objects in visual field

  • Integrate visual cues with other sensory info

  • Coordinate complex motor functions such as reaching for objects or avoiding obstacles

• Inferior Colliculi

  • Relay auditory info from cochlear nucleus to higher-order auditory areas

  • Coordinate acoustic-motor functions (ex. eye movements, head turns, etc. to auditory stimuli)

Tectum

“Ceiling” of the midbrain which contains the superior and inferior colliculi

Tegmentum

“ground” of the midbrain which contains the reticular formation, red nucleus, periaqueductal gray, and substantial nigra

• Reticular Formation

  • Sleep/Wake Cycle

  • Central core of brainstem (passes through all 3 structures and weaves together functions)

• Red Nucleus

  • Motor Coordination

• Periaqueductal Gray

  • Modulation of pain (releases endogenous opioids)

• Substantial Nigra

  • Movement

Recticular Activating System (RAS)

loops between reticular formation, thalamus, and cortex. Involved in control of arousal and conciousness. Always “on” must be inhibited by other areas for sleep

Dopaminergic Neurons in the Midbrain

• Innervates amygdala, cingulate cortex, prefrontal cortex, & nucleus accumbens

• VTA (Ventral Tegmental Area) : addiction, motivation, cognition

• SNc (Substantia nigra pars compacta) : motor control, depleted in Parkinson’s disease

Serotonergic Neurons in the Brainstem

• Raphe Nucleus

  • Where serotonin neurons lie

  • On midline of reticular formation, extends through the entire brainstem

• Innverates Everywhere!!

Norepinephrine Neurons in the Medulla and Pons

• Projects to limbic system, cortex, spinal cord, thalamus, and hypothalamus

• Locus Coeruleus

Cranial Nerves

(1) Olfactory

• Originates in olfactory epithelium (in nose), and ends in olfactory bulb

(2) Optic

• Originates in diencephalon

Midbrain

• (3) Oculomotor

• (4) Trochlear

Pons

• (5) Trigeminal

• (6) Abducens

• (7) Facial

• (8) Vestibulocochlear

Medulla

• (9) Glossopharyngeal

• (10) Vagus

• (11) Acessory

• (12) Hypoglossal

Olfactory Cranial Nerve

• CN 1

• Type: Sensory

• Function: Smell

Optic Cranial Nerve

• CN 2

• Type: Sensory

• Function: Vision

Oculomotor Cranial Nerve

• CN 3

• Type: Motor

• Function: Eyelid/Eyeball/Lens/Pupil Movement

Trochlear Cranial Nerve

• CN 4

• Type: Motor

• Function: Turn eyes down, lateral

Trigeminal Cranial Nerve

• CN 5

• Type: Sensory & Motor

• Function: Face and mouth sensations; chewing

Abducens Cranial Nerve

• CN 6

• Type: Motor

• Function: Moves eyes lateral

Facial Cranial Nerve

• CN 7

• Type: Sensory & Motor

• Function: Facial Muscles, tears, saliva, taste

Vestibulocochlear Cranial Nerve

• CN 8

• Type: Sensory

• Function: Sense of equilibrium, hearing

Glossopharyngeal Cranial Nerve

• CN 9

• Type: Sensory & Motor

• Function: Taste

Vagus Cranial Nerve

• CN 10

• Type: Sensory & Motor

• Function: Thoracic and abdominal sensation, controls speech, swallowing, gag reflex, heart rate

Accessory Cranial Nerve

• CN 11

• Type: Motor

• Function: Head and Shoulder Movements

Hypoglossal Cranial Nerve

• CN 12

• Type: Motor

• Function: Tongue movement, speech articulation