Peripheral Nervous System

The peripheral nervous system includes the cranial nerves (connected to brain innervate the head), spinal nerves (connected to spinal cord innervates the rest of the body), and ganglia (collections of neuron cell bodies in the PNS).

Functional subdivisions of the nervous system: Sensory: - somatic (skin, fascia, joints, skeletal muscles) - Visceral (organs) Motor: - somatic (skeletal muscle) - Autonomic (cardiac muscle, smooth muscle, glands)

Together, the CNS and PNS perform three general functions: - Collecting information: specialized PNS structures called receptors (dendrite endings of sensory neurons or cells) detect changes in the internal or external environment and pass them on to the CNS as sensory input - Processing and evaluating information: after processing sensory input, the CNS determines what, if any, response is required - Responding to information: after selecting appropriate response, the CNS initiates specific nerve impulses (rapid movements of an electrical charge along the neurons plasma membrane), called motor output. Motor output travels through structures of the PNS to effectors (the cell that receives impulses from motor neurons: muscle or glands)

- The peripheral nervous system includes the cranial nerves (connected to brain innervate the head), spinal nerves (connected to spinal cord innervates the rest of the body), and ganglia (collections of neuron cell bodies in the PNS). - Central nervous system - brain and spinal cord

- Peripheral nerves: extensions of cranial and spinal nerves - Each nerve is a cable-like structure that contains many axons that sometimes referred to as fibers. Within a nerve, each axon is surrounded by a layer of connective tissue called the endoneurium. The axons are bundled together into groups called fascicles. Each fascicle is wrapped in a layer of connective tissue called the perineurium. Finally, the entire nerve is wrapped in a layer of connective tissue called the epineurium

Spinal nerves is formed from union of thousands of motor and sensory axons. The spinal cord and its attached spinal nerves serve two important functions. They are a pathwat for sensory and motor impulses. The spinal cord and spinal nerves are responsible for reflexes, which are our quickest reactions to a stimulus. Two pairs of nerve roots extend from each segment of the spinal cord. • The ventral roots (anterior roots) allow motor neurons to exit the spinal cord. • The dorsal roots (posterior roots) allow sensory neurons to enter the spinal cord. • Along each dorsal root is a small bulge called the dorsal root ganlion (spinal ganglion). Inside the ganglia are the cell bodies of the sensory neurons. The dorsal and ventral nerve roots fuse to form a spinal nerve • Opening between the vertebrae called intervertebral foramina allow the spinal nerves to enter and exit the vertebral column • Gives of recurrent meningeal branches, and then divides immediately into dorsal and a ventral ramus • The dorsal ramus passes backwards and supplies the intrinsic muscles of the back and the skin covering them • The ventral ramus innervates the anterior and lateral portions of the trunk, the upper limb and lower limb Spinal nerves consist of two types of nerves: • Sensory nerves: - Deliver information to your spinal cord from muscles and joints about your body position. They also transmit sensations such as touch, pressure, pain and temperature, which experience on the surface of your skin. This information enters your spinal cord via your posterior grey horn, it is then passed to the spinal tracts and transmitted up to the brain • Motor nerves: - Pass information received from your brain through your spinal tracts to your skeletal muscles to direct precise voluntary movement

• The brachial plexus services the pectoral girdle and upper limbs • The lumbar plexus services the anterior and medial thigh • The sacral plexus services the remainder of the lower limb Brachial plexus: Which ventral rami contribute? C5-T1 The 5 major branches? Axillary nerve (innervates deltoid and teres minor muscles), median nerve (innervates anterior forearm muscles(pronator teres)), musculocautaneous nerve (innervates coracobrachialis, biceps brachii, and brachialis), radial nerve (posterior arm muscles (triceps brachii)), ulnar nerve (anterior forearm muscles (flexor carpi ulnaris and intrinsic hand muscles (palmar interossei) Lumbar plexus: Which ventral rami contribute? L1-L4 The 2 major branches? Femoral Nerve (quadriceps femoris, sartorius) and Obturator nerve (adductors brevis, longus and magnus and gracilis Sensory supply in the hand Median, ulnar and radial Sacral Plexus: Which ventral rami contribute? L4-S4 The 5 major branches? Tibial nerve (posterior thigh muscles (long head of biceps femoris)and posterior leg muscle (solecus)), common fibular nerve (short head of biceps femoris), superficial fibular nerve (fibularis longus), deep fibular nerve (tiabialis anterior