2.) List the major parts of the brain and their functions.
The four major parts of the brain are the cerebrum, diencephalon, cerebellum, and brainstem. The cerebrum, described above, has a wide range of functions, ranging anywhere from memory to controlling voluntary responses, as well as learned motor movements. It is divided into two major hemispheres, the right and the left, and the hemispheres are further divided into lobes.
The cerebellum is the part of the brain that is important in refining movements, equilibrium, and posture, as well as controls muscle tone and body position. Tumors or lesions in this area of the brain would most likely cause awkward and jerky movements.
The diencephalon is located between the midbrain and the cerebrum, and contains the thalamus, epithalamus, and hypothalamus. The hypothalamus helps to control the pituitary gland and hormone secretion, as well as plays a role in controlling eating behavior, sexual behavior, sleep, and body temperature. The epithalamus also includes the pineal gland. The function of the pineal gland in humans is still unclear, but it may aid in dark and light responses and cycles. The thalamus is known as a relay station for pain sensation and alertness.
The brainstem is the part of the brain that acts as a relay station, connecting much of the body through way of the spinal cord to the cerebrum. It is considered a ‘primitive’ structure of the brain and acts with the thalamus to control wakefulness, attentiveness, and sleep patterns. It is composed of the midbrain, pons, and medulla oblongata. The midbrain aids in controlling ocular motion. The pons aids in controlling eye and facial movements, facial sensation, hearing, and balance. The medulla oblongata is associated with breathing, blood pressure, heart rhythms, and swallowing.
(brainstem located in red)
3.) Describe the function and structure of a neuron.
A neuron is a single nerve cell. It consists mainly of a dendrite, an axon, and a cell body that is located between the dendrite and the axon. The dendrite is a bushy, branching extension of a neuron that receives messages and conducts impulses towards the cell body. The cell body is the area that contains the nucleus. It is where ribosomes, mitochondria, and other subcellular parts do the metabolic work of cells. The axon is the extension on the neuron opposite the dendrite. It ends in branching fibers, and is a means for chemical messages to be released to other neurons, muscles, or glands. A Myelin Sheath is a layer of fatty cells that encases the fibers of many neurons. It vastly increases the transmission speed of neural impulses, as well as provides for a layer of protection for the neuron.
There are several different types of neurons. Sensory, or afferent, neurons exchange information from external sources, such as light waves or sound vibrations into electrical impulses. Motor, or efferent, neurons help enable movement by their connections between dendrites to other neurons, and axons to muscles and glands. Connector, or interneurons, are neurons that are connected to other neurons forming a neural pathway.
4.) Compare and contrast the structure and function of neurons to that of neuroglia.
Neurons are neural cells that are used to form a sensory pathway throughout the body system. They consist of two main ‘pathways,’ the dendrite, and the axon with a cell body in the middle. However, neuroglia are ‘supporting cells’ for the neurons, and often have several different forms. There are four types of neuroglia; astrocytes, microglia, oligodendroglia, and Schwann cells. For the most part, each of these types of neuroglia have their own unique shape and function, depending on where they are located. Astrocytes typically cover surfaces of capillaries of the brain, and help form a blood-brain barrier which aids in the regulation of the passage of nutritive and chemical molecules to the brain neurons. They are able to influence diffusion rates and provide an opportunity for active transport. They are somewhat similar in structure to neurons, but do not have a dendrite or axon; instead, they have extended “feet” that create a ‘star’ shape.
The specific functions of oligodendrocytes are unknown; they cover the exposed surfaces of neurons and aid in holding the nerve fibers together. Like astrocytes, they have slender extensions, although oligodendrocytes do not have as many extensions as astrocytes. Their cell bodies are smaller, and typically rounder in shape.
Microglia are actually phagocytotic white blood cells that have migrated through the capillaries and serve as moving defense mechanisms for the central nervous system. They are smaller than the other glial elements, and have many fine branches that are extensions of the cell body.
The function of Schwann cells, or ependymal cells, is also somewhat ambiguous. However, experimental evidence suggests that they function as sensory receptors monitering the condition of the cerebrospinal fluid. They are cuboidal to columnar in form, and may be covered with microvilli.
5.) List the divisions of the nervous system and their major functions.
The nervous system is divided into two major parts; the central nervous system, and the peripheral nervous system. The central nervous system consists of the brain and spinal cord. The brain receives sensory input from the spinal cords and nerves and processes the various sensory inputs to initiate appropriate motor outputs. It also stores the information for later use. The spinal cord conducts the sensory information from the peripheral nervous system to the brain, and conducts motor information from the brain to the various muscles and glands.
The peripheral nervous system includes the nerves and ganglia located outside of the brain and spinal cord, the craniospinal nerves, and the autonomic nervous system, although the systems are all so close together that they almost overlap. The peripheral nervous system allows signals to travel between the central nervous system and the body’s sensory receptors. The autonomic nervous system controls basic involuntary functions of the body, such as heart beat, digestion, breathing, and blood flow.
6.) Distinguish between sensory and motor pathways.
Sensory pathways are nerve pathways that conduct afferent impulses and stimuli from the sensory organs and nerves to the spinal cord. The spinal cord then relays the sensory information to the brain, which then sorts it out and sends out an appropriate efferent response through the motor pathways to the muscles and glands, instructing them on how to react to the stimulus.
7.) List the 12 cranial nerves and their functions
The twelve cranial nerves are the olfactory nerve, the optic nerve, the oculomotor nerve, the trochlear nerve, the trigeminal nerve, the abducens nerve, the facial nerve, the acoustic nerve, the glossopharyngeal nerve, the vagus nerve, the spinal accessory nerve, and the hypoglossal nerve.
The olfactory nerve, the first cranial nerve, carries special sensory information that is responsible for the sense of smell. The optic nerve, or the second nerve, carries visual information from the sensory ganglia in the eyes, while the oculomotor nerve (#3), is the primary source of movement in the eyeball, accommodates the lens, and raises the upper eyelid. The trochlear nerve (#4), is the smallest of the cranial nerves and also aids in the movement of the eye. The fifth cranial nerve is the trigeminal nerve, which is the largest cranial nerve and responsible for sensations in the face, scalp, teeth, lips, eyeballs, nose, tongue, and throat lining, as well as for chewing. Next is the abducens nerve (#6), which also aids in the movement of the eyeball. The seventh nerve is the facial nerve, which is responsible for taste, facial expressions, and the salivatory glands. The acoustic nerve (#8) aids in hearing and balance, while the glossopharyngeal nerve (#9) is related to taste, swallowing, and blood pressure receptors. The tenth nerve is the vagus nerve, which contain chemoreceptors, pain receptors, sensations, taste, heart rate and stroke volume, peristalsis, air flow, and speech and swallowing. The spinal accessory nerve (#11), is responsible for head rotation, while the twelfth nerve, the hypoglossal nerve, aids in speech and swallowing.
8.) Describe the structure, function, and location of the thalamus and the hypothalamus.
The thalamus and the hypothalamus are both typically ‘classified’ as being included with the diencephalon. The diencephalon is located between the midbrain and the cerebrum, and includes the thalamus and hypothalamus. The thalamus is known as a relay station for pain sensation and alertness, and looks like a small, gray, oval mass in the middle of the brain. The hypothalamus is located beneath the thalamus and connects the endocrine and nervous systems. It helps to control the pituitary gland and hormone secretion, as well as plays a role in controlling eating behavior, sexual behavior, sleep, and body temperature.
9.) What is the function of the cerebrospinal fluid and the meninges? Why are there three layers in the meninges?
The cerebrospinal fluid and the meninges both serve to have one basic function: protection. The cerebrospinal fluid surrounds the brain, providing support and cushioning the brain and spinal cord. The main function of the meninges is protection, also. The three layers of meninges serves to separate the brain and spinal cord from the body cavities in which they lie and aid in support and protection. They are composed mostly of white fibrous connective tissue. The meninges around the brain and spinal cord have three layers, in order to have increased protection. The innermost layer, the pia mater, is a thin, compact membrane that closely adapts to the brain and spinal cord and also serves to provide nutrition and provides a blood source for the tissues. The middle layer, the arachnoid layer, is less dense than the outside layer and is weblike in appearance, providing a soft cushion. The outermost layer, the dura mater, is hard, tough, and dense, protecting against a blow to the head.
10.) Discuss the functions of neurotransmitters. Name the two general types of these chemicals and give examples of each.
Neurotransmitters are certain chemicals that are released when an electric pulse reaches the end of an axon branch. These chemicals diffuse across a synaptic gap, and are picked up by receptor chemicals on the end of the dendrites of a neighbor neuron. The process of absorption to the new cell changes the state of the electrical pulse flowing through the neuron. If there are enough signals coming through to the neuron cell from its neighbor neurons, this generates a big enough charge to generate a new pulse in the neuron, thus sending it on and repeating the process in a new cell.
The two general types of neurotransmitter chemicals are exciter neurotransmitters and inhibitor neurotransmitters. An example of an exciter neurotransmitter is norepinephrine, which is important in the brain and in portions of the autonomic nervous system. An example of an inhibitor neurotransmitter is dopamine, which is a central nervous system inhibitor.