Unit 2 - Subcortical systems, neurochemistry and brain function

Transcription

1 Unit 2 - Subcortical systems, neurochemistry and brain function Subcortical anatomy: Most of the five major subdivisions of the brain are subcortical. I. Telencephalon (cortical - part of forebrain) - also contains and, which are subcortical II. Diencephalon (, - part of forebrain) III. Brainstem - mesencephalon ( ) - metencephalon (, - part of hindbrain) - myelencephalon ( - part of hindbrain) 1

2 I. Subcortical telencephalon: basal ganglia - corpus striatum (caudate nucleus and putamen) - globus pallidus (together with putamen - called ) - nucleus accumbens (ventral part of striatum) - Caudate nucleus 2

3 I. Subcortical telencephalon: basal ganglia (continued) - putamen Corpus callosum Lateral ventricle Putamen - Globus pallidus Corpus callosum Caudate Thalamus Globus pallidus Anterior commissure Putamen Basal ganglia generally involved in. 3

4 I. Subcortical telencephalon: basal ganglia (continued) - nucleus accumbens (ventral striatum - involved in ) Thalamus Hypothalamus Caudate Putamen Globus pallidus 4

5 I. Subcortical telencephalon: limbic system

6 I. Subcortical telencephalon: limbic system (continued) - hippocampus and amygdala (with fornix) Corpus callosum fornix Hippocampus Amygdala Anterior commissure - cingulate gyrus 6

7 I. Subcortical telencephalon: limbic system (continued) Cingulate gyrus fornix putamen caudate ic cc GP Amygdala Mammillary body Hippocampus Limbic structures generally involved in the regulation of motivated behaviors (feeding, fleeing, fighting, sexual behaviors) and learning/ memory. - amygdala associated with - hippocampus associated with. - septal nuclei associated with. - fornix connects septal nuclei and hippocampal formation (fimbria-fornix) - fornix also provides hippocampal output to hypothalamus (mammillary bodies). 7

8 II. Diencephalon composed of and Thalamus: major relay station between sensory inputs to the brain and neocortex (for most sensory systems) - layer VI of neocortex provides significant feedback to thalamus Massa intermedia Cross-section through thalamus shows massa intermedia, a major thalamic fiber decussation system across third ventricle. 8

9 II. Diencephalon (continued) Hypothalamus: important in the control of - note the proximity of the pituitary gland, connected to the hypothalamus via the 9

10 III. Brainstem: Thalamus Midbrain - midbrain (mesencephalon) contains (below and above aqueduct, respectively) -Colliculi: -PAG ( ) -Reticular formation: -Red nucleus: -Substantia nigra: 10

11 III. Brainstem: Pons and cerebellum - pons contain nuclei for several - divided into a ventral portion (basis pontis) and a dorsal aspect (tegmentum) - basis pontis a major relay of - tegmentum contains reticular formation, tracts, and cranial nuclei Tegmentum Basis pontis 11

12 III. Brainstem: Medulla oblongata: contains several tracts, nuclei of reticular formation and several cranial nerves, much like pons. - Example: Hypoglossal nerve (XIIth cranial nerve): origin of neurons innervating muscles of the tongue. - Example: pyramids - begins in precentral gyrus, enters internal capsule to join cerebral peduncle, forms pyramids, decussates and enters spinal cord as corticospinal tract (lateral funiculus) 12

13 Basic chemistry and biochemistry - building blocks of biology Remember Star Trek? We are carbon-based creatures, as compared to other extraterrestrial races (if any exist)!!! The chemical elements (periodic table) in nature combine in various ways to form molecules (compounds). - most common elements in biochemical compounds are: C - O - H - N - - other less common by very important ones are: S - P - Most of the cellular components in our body are made of carbon containing molecules. Atoms: smallest particle (unit) of an element that maintains the properties of that element. What are atoms made of? Molecules are formed when 2 or more atoms combine. Examples: When more than one compound are mixed together, these are called mixtures; these are most often found in nature, including our body. Examples: What are ions? 13

14 Three (3) basic types of complex molecules that are important for cellular structure and function: lipids, proteins, and nucleic acids Each of these complex molecules is made up of essentially a long chain of a simpler molecule. 1. Lipids: made up of. - stored in fat cells (adipose cells) which serve as. - also very important in the formation of. - normally made up of a charged and the. - there are 3 different types of membrane lipids: phospholipids, glycolipids, and cholesterol. What are phospholipids (phosphoglycerides)? carbon chains glycerol phosphate Lipids can interact in different ways depending on the medium around them: - aqueous (polar) solvents (such as water) - non-aqueous (organic) solvents (such as chloroform) 14

15 micelle bilayer inverted micelle In aqueous solvent In organic solvent Normally, phospholipids aggregate as shown in top center to form cell membranes ( ). 2. Proteins: made up of long chains of (called residues). - proteins play a role in nearly every biological function known ( ) different amino acids serve as the building blocks of proteins. - each amino acid is made up of, a, and a, which differentiates amino acids. - amino acids can be combined in any order (variety of proteins). - short chains are called:. - long chains are called:. amino group carboxyl group side chain 15

16 Examples of different amino acids; notice the different side chains Proteins are said to have structures: - primary structure: - secondary structure: - tertiary structure: - quaternary structure: Also, proteins are said to have different domains (examples: extracellular domain, intracellular domain, transmembrane domain, binding domain). 16

17 Examples of secondary structures based on á-helix and â-sheet á-helix â-sheet Many proteins are associated with the cell membrane: - integral proteins have peptide domains that insert, once or several times. 17

18 3. Nucleic acids (DNA, RNA): - the blueprint of life. - as with amino acids, nucleotides combine in any order. - only four different types of nucleotides (slightly different for DNA and RNA). - single nucleotides made of three components: a. b. c. Base Phosphates Deoxyribose The 4 bases of DNA 18

19 Protein synthesis Where are proteins produced in our body? How does a cell know how to make a particular protein? - It needs to begin with a code which tells the cell which amino acids to string together to make a particular protein. - That code is provided by a gene (blueprint of life). - It is believed that the genome contains approximately 60,000 genes (Human Genome Project). - Question: Do all cells in our body have the same genes (i.e. genetic code)? - Question: Are all stretches on DNA part of genes? Major steps in protein synthesis: DNA fi mrna fi protein 1. : make an mrna copy of a specific gene (in nucleus) 2. mrna transported to cytoplasm (outside of nucleus) 3. : use code from mrna to build a protein (successive triplets (3 nucleotides) code for one of 20 amino acids to be linked. 19

20 Illustrated steps of protein synthesis Puzzle: What makes a liver cell different from a neuron? Protein synthesis is an ongoing dynamic process. 20