BCSC 240 Neurobiology Exam 1 - Gross Organization I

Central Nervous System

• Located inside of bone

• Includes the brain (in the skull) and the spinal cord (in the backbone)

• Interprets sensory input, initiates movement, and mediates complex cognitive processes

Peripheral Nervous System

• Located outside of bone

• Includes nerve

• Serves to bring sensory information into the CNS (called afferents) and carry motor signals out from the CNS (efferents)

The central nervous system is primarily composed of what two parts?

The central nervous system is primarily composed of the brain and the spinal cord. Anything that is located inside the bone is part of the central nervous system

What are the two components of the peripheral nervous system and what do they break down into?

The two main components of the peripheral nervous system are:

• The Somatic Nervous System (External Environment)

  • Afferent Nerves

    • These are all for sensory input, so anything that has to do with the senses

  • Efferent Nerves

    • These are all for motor output and aids in moving the muscles and everything else

• The Autonomic Nervous System (Internal Environment)

  • Afferent Nerves (Sensory Stuff Inside the Bone)

    • Sensory stuff inside the bone

  • Efferent Nerves (Going to Muscle in Internal Environment)

    • Sympathetic Nervous System

      • Aids in preparing the body for fight or flight mode

    • Parasympathetic Nervous System

      • Aids in preparing the body for rest and digestion

What is the somatic nervous system?

The somatic nervous system is a subgroup of the Peripheral nervous system. It is comprised of afferent nerves and efferent nerves. It deals with the external environment. Afferent nerves comprise of sensory input, and efferent nerves comprise of motor output

What is the autonomic nervous system?

The autonomic nervous system is a subgroup of the Peripheral nervous system. It is comprised of afferent nerves and efferent nerves. It deals with the internal environment and deals with stuff happening under the hood. Efferent nerves comprise of both the sympathetic nervous system and the parasympathetic nervous system. The former deals with the fight or flight mode, and the latter deals with rest and digestion

Explain the functions of efferent and afferent nerves in the somatic nervous system

All deal with the external environment

• Afferent Nerves: Sensory Input (taste, touch, hear, see, smell)

• Efferent Nerves: Motor Output (skeletal motor system going out)

Explain the functions of efferent and afferent nerves in the autonomic nervous system?

All deal with the internal environment

• Afferent Nerves: Not really explained but bringing sensory info into the CNS

• Efferent Nerves: Going to muscle in internal environment

  • Sympathetic nervous system

    • Fight or flight mode

  • Parasympathetic nervous system

    • Rest and digestion

What are the anatomical references of an organism?

• Anterior/Rostral

  • Towards the front/nose

• Posterior/Caudal

  • Towards the back/tail

• Dorsal

  • Towards the top

• Ventral

  • Towards the bottom

• Medial

  • Towards the middle

• Lateral

  • Towards the side

Explain the differences between ipsilateral and contralateral?

Structures on the same side of the head are said to be ipsilateral. Structures on the opposite side of the head are then contralateral

What are the anatomical directions in humans?

In humans, the directions in the cerebral hemispheres are rotated by 90 degree angles in comparison to those in the spinal cord (and brain stem) because of the unusual upright posture of humans. Thus, for example, the top of the head and the back of the body are both dorsal even though the directions are different

• Refer to slide on Gross Organization I

Anatomical reference for the top of the head?

Dorsal

Anatomical reference for the bottom of the head?

Ventral

Anatomical reference for the front of the head?

Anterior/rostral

Anatomical reference for the back of the head?

Posterior/caudal

What are the planes of the section of the brain?

A slice of the brain is called a section

• sagittal - cut that separates brain from left to right

• horizontal - cut that separates brain from top to bottom

• cut that separates brain from the front to back

A cross-section is cut at a right angle to a long narrow structure (i.e., the spinal cord)

What are the main parts of the brain?

The main parts of the brain are the cerebrum, the cerebellum, and the brain stem

What is the cerebrum and its main function?

The cerebrum is the top-most portion of the brain that is split into two cerebral hemispheres that each receive sensory input and motor output from the opposite side of the body. The left hemisphere controls the right side, the right hemisphere controls left side

What is the cerebellum and its main function?

The cerebellum is behind/below the cerebrum and primarily serves for motor coordination. It is also divided into two hemispheres and each side controls its respective side

What is the brain stem and its main function?

The brain stem forms the stalk from which the cerebrum and cerebellum sprout, fibers of passage, cranial nerves, basic functions (e.g., breath rate)

• Sensory input, motor output control of the head

• Controls things such as smiling and does not directly go down into the spinal cord to process input

What are the convoluted surface areas of the cerebrum?

The cerebrum has a lot of surface to allow for more cortical surface to exist in the confines of a smaller cranium

• Fissures: large grooves

• Sulci: small grooves

• Gyri: bumps

What are the major fissures of the cerebrum?

• Longitudinal: Separates the cerebrum from left to right

• Central: Look at image in Gross Organization I

• Lateral: Look at image in Gross Organization I

These major fissures partially divide each hemisphere into four lobes: frontal, parietal, temporal, and occipital

What are the large gyro in the cerebrum?

The three large gyri are: precental, postcentral, and superior temporal

What connects the two hemispheres of the cerebrum together?

The cerebral hemispheres are connected by several fiber tracts called commissures

• The largest commissure is called the corpus callosum. It is visible if the two hemispheres are gently pulled apart at the longitudinal fissure

What can be learned from viewing a frontal section of the cerebrum?

• Shows that the cerebrum comprises of three different areas:

  • outer area of neuronal cell bodies (called gray matter or cerebral cortex)

    • Outer Area - Cell Bodies

  • inner area of myelinated axons (called white matter)

    • Inner Area - Myelinated Axons

  • subcortical areas of gray matter

The brain also contains fluid-filled caverns and canals, called the ventricular system. The cerebrum surrounds the paired, lateral ventricles

What is the overall functions of the cerebellum?

The cerebellum, like the cerebrum, is a highly folded structure of two hemispheres, each of which is divided into lobes. Each ridge or gyrus is called a folium, with gray matter at the edge and white matter inside

The brain stem consists of what divisions?

Four Main Divisions:

• Diencephalon (either side of third ventricle): Uppermost region of the brain stem

  • Thalamus

  • Hypothalamus

• Midbrain (cerebral aqueduct): Middle region of the brain stem

  • Tectum

    • Located above the tegmentum

  • Tegmentum

    • Located below the tectum

• Pons (below 4th ventricle)

• Medulla (below 4th ventricle)

  • Medulla is continuous with the spinal cord

Explain the cranial nerves in the brain stem

The brain stem has 12 pairs of cranial nerves that can be observed, most of which emerge from the brain stem. The cranial nerves provide sensory and motor innervation mainly to structures in the head and neck. Note that the axons from the eyes (optic nerve) cross (or decussate) as necessary as the optic chasm prior to entering the brain

What main methodologies are used to detect the brain structures?

• Computer tomography (CT)

  • Measures opacity to X-rays

• Magnetic resonance imaging (MRI)

  • Measures hydrogen atom response to magnetic fields

  • Basically detects water

  • Allows us to see connectivity and where the axons are going

What main methodologies are used to reveal functional organization of the brain?

• Positron Emission Tomography (PET)

  • inject a radioactive substance

  • have subject perform behavior (active cells take up substance)

  • scan a horizontal slice of brain

• Functional Magnetic Resonance Imaging (fMRI)

  • no substance injected

  • have subject perform behavior (active cells need more oxygen/glucose)

  • scan brain for de/oxygenated hemoglobin