Analysis of the Nervous System (3 aspects)

• Systems Neuroscience: investigates groups of neurons that preform a common function

• Behavioral Neuroscience: looks at the interaction among systems that effect behavior (looking at the output), behaviors influenced by environment and society

• Cognitive Neuroscience: looks in the fields of thinking, learning and memory

Central Nervous System: composed of the brain system and spinal cord

Peripheral Nervous System: composed of peripheral nerves, spinal and cranial nerves

Neuron = the functional unit of the nervous system

• Neuron Theory: functions of the nervous system reflects the function of individual neurons, group of neurons and their connections

• Bipolar Neuron: special senses of the face…found in retina, olfactory, ear (eyes & ears) , sensory info to brain

  • Synapses on neurons in dorsal horn

• Pseudo-unipolar Neuron: sympathetic ganglion, sensory info to the brain …found in sympathetic ganglia

• Multipolar Neuron: (most common neuron image) motor neurons…found in distal PNS

  • Synapses on skeletal muscle cells

GREY vs WHITE
Grey Matter: Ganglia, Nuclei, Cortex (information is integrated in gray matter)

(outside cortex)
White Matter: Tract, Lemniscus, Fasciculus, Column, Peduncle, Capsule (internal cortex...doing various functions) (aka the highs for information to travel)

Central Nervous System

Gila of the CNS: these cells out number neurons

• Astro: help support grey matter…Others support BB

• Micro-G: scavengers, remove plaques in the brain

• Ependyma: Formation and movement of spinal fluid & lining of ventricles

• Oligodendrocytes: myelinate nerves of the CNS

Spinal Cord

• Composed of horns & columns

• Information comes in through the posterior and "exits"  anteriorly

• Within the cross section of the spinal cord you can see what looks like the letter "H" which is composed of Grey matter (Ganglia, Nuclei, Cortex…information is integrated in gray matter), this is then divided into dorsal, lateral and ventral horns

  • These Horns contain cell bodies of motor neurons, interneurons and the ends of sensory neurons

  • Leading to these horns are columns which are composed to bundle of nerves transmitting signals

Dorsal region: contain interneurons and the ends of sensory neurons

Lateral region: autonomic cell bodies

Ventral region:  bodies of motor neurons and interneurons

• Columns transmit signals from the horns

2 Main Functions of the Spinal Region:

1. Conveys information from the peripheral regions to the Brian

2. Processes Information

Brainstem:

• motor and sensory fiber tracts travel through the brainstem

• It is here that you find “subconscious control” to maintain equilibrium, cardiovascular activity , respiration and other functions

• Composed of 3 sections: Mid-brain, Pons and Medulla Oblongata

  • Mid-brain: where info crosses over from one side to another. Root of cranial nerve 3 & 4

  • Pons: roots of cranial nerves 5,6,7,8

  • Medulla: roots of cranial nerves 9,10,11,12. Where we find pyramidal decussation, which is the mid-line crossing of axons

Cranial Nerves (1- 12):

1. Olfactory: smell

2. Optic: vision

3. Oculomotor: moves pupil of eyes up & down, raises upper eyelid, constricts pupil

4. Trochlear: moves pupil of eye medially/down

5. Trigeminal: Facial sensation, chewing sensation of TMJ

6. Abducens: abduct pupil of the eye

7. Facial: facial expression, closes eyes, tears, salivation and taste

8. Vestibulocochlear: sensation of head position relative to gravity and head movement, hearing

9. Glossopharyngeal: swallowing, salivation and taste

10. Vagus: regulates viscera, swallowing, speech & taste

11. Spinal Accessory: elevates shoulders and turns head

12. Hypoglossal: moves tongue

__Cerebellum (aka lil brain): __

• consists of two large cerebellar hemispheres

• connects to the posterior brain-stem by peduncles (large bundles of fibers)

• function is to coordinate movement…smooth and accurate movements, maintain posture, movement of head in space

Cerebellar Connections:

Vestibulocerebellum (Flocculonodular Lobe): detects head position relative to gravity…coordinates with inner ear & postural reflexes to keep us upright while we sit/move.

Spinocerebellum/Spinal Cord: checks the sensory input from the spinal cord and that it matches the motor output…if not the cerebellum will correct/override

Cerebrocerebellum/ Cerebral Cortex: communicates with the cerebrum and is the final check to the movement being sent out

Cerebrum

• consists of cerebral hemisphere and diencephalon

• suface = cerebraal cortex

• the site of cognitive thinking…so reasoning, language, non-verbal communication, intelligence and personality

The cerebrum is divided by the longitudinal fissure into 2 cerebral hemispheres.

• Elevations on the surface = gyri

• Grooves on the surface = sulci

The Diencephalon is composed of 4 parts

• Thalamus: processes emotional and some memory information, integrates different sensations, regulates consciousness, arousal & attention…essentially processes sensory information and relays a motor response

• Hypothalamus: maintains body temperature, metabolic rate and chemical composition of tissues & fluids (communicates with endocrine gland to regulate secretions)

• Epithalamus: influences the secretions of other endocrine glands

• Subthalamus: part of the neural circuit control movements (aids in movement control)

  The Cerebral Hemispheres are each divided into 6 lobes (regions have specific functions)

  • Frontal

  • Parietal

  • Temporal

  • Occipital

  • Limbic

  • Insular

• The basal ganglia in the cerebral hemispheres is composed of the: Caudate, Putamen and Globus Pallidus

  • Putamen & Globus Pallidus = Lenticular nucleus

  • Caudate & Putamen = Corpus Striatum

  • Subthalamic Nucleus: basal ganglia neural circuit

• The Hippocampus and Amygdala: apart of the limbic system…processes emotions and memory

  • involved with processing emotions/emotional response

  • Hippocampus function = turning working memory to long lasting memory

Peripheral Nervous System

Afferent axons: carries info TOWARDS CNS

Efferent axons: carries info AWAY from CNS

2 divisions: __Somati__c vs Autonomic

• Somatic: conscious about it feel it, act on it…axons, sensory nerve endings, myelin

• Autonomic: nerve endings on our organs…automatically functioning, we are not conscious about  entire neurons, sensory nerve endings, synapses, ganglia

Organization of the PNS

• Described based on the functional components of the fibers they carry

  • Sensory fibers bring info to the CNS (AFFERENT)

    • Spinal dorsal root ganglia & Cranial Nerve Ganglia

    • Precise Information coming in from a specific area on the body(Soma)

    • Information regarding

      • Pain

      • Light Touch

      • Temperature

      • Vibration

      • Position in Space (Proprioception)

  • Motor fibers carry info towards the PNS/Muscles (EFFERENT)

    • Spinal Cord (spinal nerves) & Brainstem (cranial Nerves)

    • What we want to do.. the reaction…produces movement

    • Under direct voluntary control

    • From the ventral/anterior portion …spine to muscles

    • Weakness in muscles can be caused by innervation issue

All SOMATIC: "What we know we're doing"

Autonomic

• Innervates hollow organs (blood vessels, glands, heart, lungs, liver, GI)

• Effects smooth muscle contraction…absence of excitation = dilation

• Direct innervation of some glands and nodal tissue of the heart

• Parasympathetic & Sympathetic: have opposing effects on hollow organs

  • Sympathetic: fight or flight…pupils dilate, HR increases, airways dilate, blood directed away from GI & towards skeletal muscles, ejaculation

  • Parasympathetic: Rest & Digest (homeostasis) pupils constrict, HR decreases, Increase in GI blood flow and motility, blood to genitals increase

Cerebrospinal Fluid System: Ventricles and Meninges

CFS: modified filtrate of plasma, circulates from cavities in the brain to the surface of CNS into the venous blood system

4 ventricles:

• pair of lateral ventricles in the cerebral hemisphere

  • Communicate with the 3rd along the interventricular foramina

• Third ventricle along the midline of the diencephalon

  • Communicates/connected to the 4th by the cerebral aqueduct

• Fourth ventricle deep w/in the brainstem, posterior to the pons and medulla & anterior to the cerebellum

• Communicates with the spine, found in spinal cord

• Compression on the ducts > creates pressure within the brain

Meninges: membranous coverings

• Dura (thick)

• Arachnoid (web)

• Pia

Blood Supply

• 2 main arteries: Internal carotids & Vertebral arteries (posterior)

• Vertebral fuse to create basilar > brainstem and cerebellum

• Circle of Willis (anastomotic ring): supplies to the cerebral hemispheres

  • Anterior communicating (R-L) frontal

  • Posterior communicating, blood can be brought forward and back

• 3 majors to the Cerebral Hemispheres

  • Anterior - branch of the internal carotid

  • Middle - branch of the internal carotid

  • Posterior - continues from the Circle of Willis

• Blood Supply to the Nerves

  • Nerves need blood to the Vasoneurium: contain blood supply, glial cells and supporting fascia

  • Present in all Peripheral Nervous Tissue