Review on 11,12

Chapter 11 The Senses

• General senses


• Special senses

The senses in humans are a large part of our everyday life. We need them to navigate and to function properly. There are two types of sense receptors in humans, general and special senses. The general senses are pain, light touch, temperature, and position. Some of these senses are encapsulated in nerve endings and some of them are left bare or naked. There are 5 categories that senses fit into and they are mechanoreceptor, thermoreceptors, photoreceptors, and pain receptors. Given this the sensory stimuli can be internal or external.

Special senses are taste, smell, vision, hearing and balance. Taste is very important and it comes from receptor cells in the tongue that have microvilli that once food is broken down in the mouth it bonds to providing taste. There are 5 basic flavors that we taste and they are sweet, sour, bitter,salty, and umami. sweet comes from sugars, sours come from acidic, salty comes from metal ions, bitter comes from chemical substances, and umami is the meaty taste associated with MSG. Smell is acquired by receptor cells of the olfactory epithelium. Smell and taste greatly influence each other.

The visual sense is also a big part of our senses. This comes from the eye. There are 3 distinct layers of the eye and they are the outer layer, the middle layer and the inner layer. The outer layer consists of the sclera and the cornea. These allow the light to enter the eye. The middle layer is the choroid, ciliary body, and the iris. These regulate the light that enters the eye, regulates your lens allowing it to focus, and absorbes stray light.. The inner layer consists of the retina. This responds to the light converting it to nerve impulses.

Hearing and balance go hand in hand. The ear detects sound and body positions enabling us to balance. The ear consists of three parts also the outer ear, middle ear and inner ear. The outer ear is the auricle, ear lobe and external auditory canal. The auricle directs sound waves into the external auditory canal where it directs it into the ear drum. The middle ear has the ear drum and the ossicles. The ear drum vibrates and sends the vibrations to the cochlea in the inner ear. The inner ear consists of the cochlea, semicircular canals, the saccule and the utricle. This is where it gets converted to nerve impulses that detects head movement and linear acceleration.

With these senses we can navigate as best as possible in modern life. they help us communicate and understand the world around us.



Chapter 12 The Skeleton and muscles

• Structure and function of the skeleton


• Skeletal muscles

The human skeleton consists of 206 bones. Bones provide structure and give shape to the human body. They also provide protection to the internal organs. There are two parts of the skeleton, the axial and the appendicular skeleton. Bone has what is called the compact bone and the spongy bone. The spongy bone is called this because of its spongy appearance. Inside the shafts of the long bones is what is called marrow. There is red marrow called this after its color. It is found in new bornes and produces red blood cells, white blood cells and platelets that are lost each day. Over time the red marrow turns to what is known as yellow marrow.

The joints in our body are what provide the movement. There are some that are not movable but for the most part we have what is called movable joints. These are known as the ovial joints. These provide a wide degree of movement. These joints are held together by what is known as ligiments. For the most part ligiments are inflexible. Tendons and muscles also provide structure and support in joints. There are laos ball and socket joints and hinge joints. There is a surgery that is known as arthroscopic surgery that can repair damaged joints with little trauma to the joint.

The are a few things that can affect joint and they are arthritis and rheumatiod arthritis. Arthritis is caused by wear and tear on the joints causing cartilage to flake and crack causing the bones to grind together and result in swelling and pain. Rheumatiod arthritis is an autoimmune disorder where the synovial membrane gets inflammed. These affected joints can be completely immobilized and/or dislocated causing the bone to collapse. This type of arthritis occurs mostly in people between the ages of 20 and 40. Although it is a permenant condition it can be treated.

In a newborn baby the bones are bowed and are very fragile. Over time they get stronger and they form.In order for this to properly occur you need to have sufficient calcium. Over the course of your life it is likely that you will break a bone. The bones have the ability to repair themselves. Also another problem that adults face is osteoporosis. This is a problem that occurs what the bones get brittle due to lack of calcium. This usually happens in older women, people who have been bed ridden for some time, or exposure to certain metals. Also smoking can affect this disease.

The skeletal muscles

The skeletal muscles play a large part in body movement. They maintain posture in movement and while at rest. These muscles contain fibers that are excitable and contractile. These take nerve impulses to cause muscle contractions. There are what is known as slow twitch and fast twitch fibers. The fast twitch fibers are the ones that perform rapid movement and the slow twitch fibers are what perform the slower movements. Muscles can be bulked up with excersize. In doing so you can also help your endurance.