The Peripheral Nervous System The Peripheral Nervous System includes everything other than the brain and the spinal cord. It is broken down into 2 distinct parts: Cranial Nerves. We have 12 pairs of cranial nerves that control muscles in the face and neck. These nerves include: Olfactory nerves (I) – sense of smell Optic nerves (II) - vision Oculomotor nerves (III) – muscles of the eye (including pupil) Trochlear nerves (IV) – motor nerve of the eye found in all jawed vertebrates Trigeminal nerves (V) – sensations of the face, and biting and chewing Abducens nerves (VI) – lateral rectus muscles of the eye Facial nerves (VII) – facial expressions and taste sensations of 2/3 of the tongue. Vestibulocochlear nerves (VIII) – responsible for maintenance of balance and transmission of sound to the brain Glossopharyngeal nerves (IX) – taste in the posterior 1/3 of the tongue, among other functions Vagus nerves (X) – aka the wanderer. It interfaces with the parasympathetic controls of the heart and digestive systems Accessory nerves (XI) – Sternocleidomastoid muscles and the trapezius muscles of the neck Hypoglossal nerves (XII) – muscles of the tongue

The Peripheral Nervous System The Peripheral Nervous System includes everything other than the brain and the spinal cord. It is broken down into 2 distinct parts: Cranial Nerves. We have 12 pairs of cranial nerves that control muscles in the face and neck. These nerves include: Olfactory nerves (I) – sense of smell Optic nerves (II) - vision Oculomotor nerves (III) – muscles of the eye (including pupil) Trochlear nerves (IV) – motor nerve of the eye found in all jawed vertebrates Trigeminal nerves (V) – sensations of the face, and biting and chewing Abducens nerves (VI) – lateral rectus muscles of the eye Facial nerves (VII) – facial expressions and taste sensations of 2/3 of the tongue. Vestibulocochlear nerves (VIII) – responsible for maintenance of balance and transmission of sound to the brain Glossopharyngeal nerves (IX) – taste in the posterior 1/3 of the tongue, among other functions Vagus nerves (X) – aka the wanderer. It interfaces with the parasympathetic controls of the heart and digestive systems Accessory nerves (XI) – Sternocleidomastoid muscles and the trapezius muscles of the neck Hypoglossal nerves (XII) – muscles of the tongue

Peripheral Nervous System continued The other half of the PNS consists of the 31 pairs of spinal nerves that branch off the spinal cord. These nerves consist of both sensory and motors nerves that pass information to and from the brain. The PNS can be further divided into the somatic nervous system and the autonomic nervous system The somatic nervous system connects the CNS to the striated (voluntary) muscles. The autonomic nervous system goes to the glands, smooth muscle, and cardiac muscle.

The Senses Receptors of the Skin – these include touch, pressure, hot/cold, and pain. The touch receptors are found on the surface of the skin, as are the hot/cold and pain receptors. Pain receptors are not found in deep tissue. Pressure receptors are found deep in the tissue. NOTE: The skin consists of three distinct layers. The top layer (epidermis) the body’s protective layer. The middle layer (dermis) consists of connective tissue that gives the skin strength. It also has things like sweat and sebaceous glands. The bottom layer (hypodermis or subcutaneous region) contains 50% of body fat.

Senses continued Taste – taste receptors are found on the tongue (aka taste buds) and consist of receptors for bitter, sweet, salty, and sour flavours. Smell – olfactory receptors are found at the back of the nose and are part of the brain. Our sense of smell is not particularly good, but we can detect the smell of our blood relatives (mother, father, and children). A dog’s sense of smell is 1000X to 10,000,000X better than ours.

Senses continued Hearing (and balance) – our ears are divided into 3 parts: the outer ear (includes the outer ear and the auditory canal), the middle ear (includes the ear drum, and the malleus (hammer), stapes (stirrup), and incus (anvil)), and the inner ear (the semicircular canals, the auditory nerve, and the cochlea). NOTE: The inner ear is responsible, in part, for maintaining balance.

Senses continued Vision – Vision is the primary means of sensing our environment. Our eyes are the ‘cameras’ for our brain. Fun Fact: The image you see is upside down on the retina. Your brain flips it right-side up.

Your eyes The retinas of your eyes contain both rods and cones. The cones are used during daylight and can detect colours and shapes extremely well. The rods, on the other hand, do not detect colour – only shades of grey – and are very sensitive in dim light. Finding your blind spot Finding your Master (Dominant) eye